CVE-2026-89544 (GCVE-0-2026-89544)
Vulnerability from cvelistv5
Published
2026-09-11 19:44
Modified
2026-10-21 12:47
Severity ?
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: SUNRPC: fix gssx_dec_option_array error path bugs Four coupled defects in the gssx XDR option-array decoder make the error paths unsafe: a NULL deref in the caller, a refcount leak on the decoded group_info, and a latent use-after-free that the leak fix would otherwise expose. gssx_dec_option_array() sets oa->count = 1 before allocating oa->data. If that allocation fails, -ENOMEM is returned with oa->count == 1 and oa->data == NULL. All other error paths jump to free_oa: which frees oa->data and NULLs it but also leaves oa->count == 1. The caller trusts the count: gssp_accept_sec_context_upcall() gssx_dec_accept_sec_context() gssx_dec_option_array() /* fails, count=1 data=NULL */ data = res.options.data[0].value /* NULL deref */ Independently, free_creds: releases the partially decoded svc_cred with a bare kfree(creds). gssx_dec_linux_creds() installs a groups_alloc() result into creds->cr_group_info; that object is kvmalloc-backed and refcounted, and only put_group_info() reaches kvfree(). A plain kfree(creds) drops the wrapper and leaks the group_info allocation. The natural fix for the leak is to call free_svc_cred(creds) before kfree(creds), but free_svc_cred() invokes put_group_info() on creds->cr_group_info unconditionally when non-NULL. The existing out_free_groups: path in gssx_dec_linux_creds() already called groups_free() on that pointer without clearing it, so once free_svc_cred() is wired in, the subsequent put_group_info() would touch freed memory. Fix all four together: - Move the oa->count = 1 assignment below the oa->data allocation so it is never set when oa->data is NULL. - Reset oa->count to 0 at free_oa: so count and data stay coherent and the caller sees an empty option array. - Call free_svc_cred(creds) before kfree(creds) at free_creds: so the refcounted cr_group_info is released. free_svc_cred() either NULL-guards each field explicitly (cr_group_info has an if() check) or delegates to a helper that is NULL-safe itself (kfree for the string fields, gss_mech_put() which guards with if(gm) at gss_mech_switch.c:342), so it is safe to call on a partially decoded svc_cred where only cr_uid/cr_gid/cr_group_info have been written and everything else is zero from kzalloc. - In gssx_dec_linux_creds()'s out_free_groups: path, release cr_group_info with put_group_info() rather than groups_free() so the teardown matches free_svc_cred()'s refcount-aware path, and clear the pointer so a later free_svc_cred() on the same creds does not release it a second time.
References
Impacted products
Vendor Product Version
Linux Linux Version: 5e6013ae2c8d420faea553d363935f65badd32c3
Version: 3cfcfc102a5e57b021b786a755a38935e357797d
Version: 3cfcfc102a5e57b021b786a755a38935e357797d
Version: 3cfcfc102a5e57b021b786a755a38935e357797d
Version: 3cfcfc102a5e57b021b786a755a38935e357797d
Version: b97c37978ca825557d331c9012e0c1ddc0e42364
Version: bfa9d86d39a0fe4685f90c3529aa9bd62a9d97a8
Version: bb336cd8d5ecb69c430ebe3e7bcff68471d93fa8
Version: dd292e884c649f9b1c18af0ec75ca90b390cd044
Version: 934212a623cbab851848b6de377eb476718c3e4c
Version: 9806c2393cd2ab0a8e7bb9ffae02ce20e3112ec4
Version: 996997d1fb2126feda550d6adcedcbd94911fc69
Version: 6.6.23   ≤
Version: 4.19.311   ≤
Version: 5.4.273   ≤
Version: 5.10.214   ≤
Version: 5.15.153   ≤
Version: 6.1.83   ≤
Version: 6.7.11   ≤
Version: 6.8.2   ≤
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: fix gssx_dec_option_array error path bugs\n\nFour coupled defects in the gssx XDR option-array decoder make the\nerror paths unsafe: a NULL deref in the caller, a refcount leak on\nthe decoded group_info, and a latent use-after-free that the leak\nfix would otherwise expose.\n\ngssx_dec_option_array() sets oa-\u003ecount = 1 before allocating\noa-\u003edata.  If that allocation fails, -ENOMEM is returned with\noa-\u003ecount == 1 and oa-\u003edata == NULL.  All other error paths jump\nto free_oa: which frees oa-\u003edata and NULLs it but also leaves\noa-\u003ecount == 1.  The caller trusts the count:\n\n    gssp_accept_sec_context_upcall()\n      gssx_dec_accept_sec_context()\n        gssx_dec_option_array()        /* fails, count=1 data=NULL */\n      data = res.options.data[0].value /* NULL deref */\n\nIndependently, free_creds: releases the partially decoded svc_cred\nwith a bare kfree(creds).  gssx_dec_linux_creds() installs a\ngroups_alloc() result into creds-\u003ecr_group_info; that object is\nkvmalloc-backed and refcounted, and only put_group_info() reaches\nkvfree().  A plain kfree(creds) drops the wrapper and leaks the\ngroup_info allocation.\n\nThe natural fix for the leak is to call free_svc_cred(creds) before\nkfree(creds), but free_svc_cred() invokes put_group_info() on\ncreds-\u003ecr_group_info unconditionally when non-NULL.  The existing\nout_free_groups: path in gssx_dec_linux_creds() already called\ngroups_free() on that pointer without clearing it, so once\nfree_svc_cred() is wired in, the subsequent put_group_info() would\ntouch freed memory.\n\nFix all four together:\n\n  - Move the oa-\u003ecount = 1 assignment below the oa-\u003edata allocation\n    so it is never set when oa-\u003edata is NULL.\n  - Reset oa-\u003ecount to 0 at free_oa: so count and data stay\n    coherent and the caller sees an empty option array.\n  - Call free_svc_cred(creds) before kfree(creds) at free_creds:\n    so the refcounted cr_group_info is released.  free_svc_cred()\n    either NULL-guards each field explicitly (cr_group_info has\n    an if() check) or delegates to a helper that is NULL-safe\n    itself (kfree for the string fields, gss_mech_put() which\n    guards with if(gm) at gss_mech_switch.c:342), so it is safe\n    to call on a partially decoded svc_cred where only\n    cr_uid/cr_gid/cr_group_info have been written and everything\n    else is zero from kzalloc.\n  - In gssx_dec_linux_creds()\u0027s out_free_groups: path, release\n    cr_group_info with put_group_info() rather than groups_free()\n    so the teardown matches free_svc_cred()\u0027s refcount-aware path,\n    and clear the pointer so a later free_svc_cred() on the same\n    creds does not release it a second time."
        }
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            "version": "3.1"
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            {
              "lang": "en",
              "value": "AV:N - The decoder runs only as a consequence of an RPCSEC_GSS_INIT/CONTINUE_INIT Call to in-kernel nfsd (and other SUNRPC servers such as lockd) on the network, typically TCP/2049. A remote client drives svcauth_gss_proxy_init() \u2192 gssp_accept_sec_context_upcall() \u2192 gssx_dec_option_array(); the attacker\u2019s reach is purely over the network.\nAC:L - Any allocation or XDR error after oa-\u003ecount is set to 1 leaves count=1 with data=NULL, and the caller always indexes res.options.data[0]. The attacker can induce those failures by flooding pre-auth GSS_INIT upcalls that each pin 256 KB of receive pages (especially under memcg-limited nfsd) and by driving large group-list replies, so success does not depend on conditions beyond their control.\nPR:N - svcauth_gss_proxy_init() runs from svcauth_gss_proc_init() on the first RPCSEC_GSS handshake leg, before the kernel has validated any Kerberos ticket. The upcall and option-array decode execute for an unauthenticated NFS client; no local account or prior credential on the server is required.\nUI:N - The crash is triggered entirely by an inbound RPC to an already-running nfsd/SUNRPC service thread. No administrator or end-user action such as mounting a filesystem or opening a file is required.\nS:U - The NULL dereference and group_info leak occur inside the host kernel\u2019s SUNRPC/GSS code. Impact stays within that kernel\u2019s security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:N - With oa-\u003ecount==1 and oa-\u003edata==NULL, gssp_accept_sec_context_upcall() does \u0026res.options.data[0].value, a NULL+small-offset load that faults on the unmapped zero page. No kernel memory is returned to the attacker; unlike a UAF, freed object contents are never read.\nI:N - The faulting access is a pure NULL-pointer dereference with no kernel write. The put_group_info() UAF described in the fix is only latent: the unpatched free_creds path kfree()s the svc_cred wrapper without touching cr_group_info, so the dangling pointer is not used.\nA:H - The NULL dereference oopses the nfsd (or lockd) thread and panics the host where panic_on_oops is set, which is typical on NAS/appliance NFS servers. The same error path also leaks the kvmalloc-backed group_info, and the crash can be repeated to take down SUNRPC service threads."
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        "dateUpdated": "2026-10-21T12:47:49.203Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/8c56a46db3b7523f13e167c3e2c6e3c47a87dcb3"
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          "url": "https://git.kernel.org/stable/c/fb30241f7ccace372ee83017891549f23a715581"
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      "title": "SUNRPC: fix gssx_dec_option_array error path bugs",
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    "cveId": "CVE-2026-89544",
    "datePublished": "2026-09-11T19:44:20.424Z",
    "dateReserved": "2026-09-11T19:38:34.722Z",
    "dateUpdated": "2026-10-21T12:47:49.203Z",
    "state": "PUBLISHED"
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    "vulnrichment": {
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A remote client drives svcauth_gss_proxy_init() \\u2192 gssp_accept_sec_context_upcall() \\u2192 gssx_dec_option_array(); the attacker\\u2019s reach is purely over the network.\\nAC:L - Any allocation or XDR error after oa-\u003ecount is set to 1 leaves count=1 with data=NULL, and the caller always indexes res.options.data[0]. The attacker can induce those failures by flooding pre-auth GSS_INIT upcalls that each pin 256 KB of receive pages (especially under memcg-limited nfsd) and by driving large group-list replies, so success does not depend on conditions beyond their control.\\nPR:N - svcauth_gss_proxy_init() runs from svcauth_gss_proc_init() on the first RPCSEC_GSS handshake leg, before the kernel has validated any Kerberos ticket. The upcall and option-array decode execute for an unauthenticated NFS client; no local account or prior credential on the server is required.\\nUI:N - The crash is triggered entirely by an inbound RPC to an already-running nfsd/SUNRPC service thread. No administrator or end-user action such as mounting a filesystem or opening a file is required.\\nS:U - The NULL dereference and group_info leak occur inside the host kernel\\u2019s SUNRPC/GSS code. Impact stays within that kernel\\u2019s security authority; no VM, IOMMU, or sandbox boundary is crossed.\\nC:N - With oa-\u003ecount==1 and oa-\u003edata==NULL, gssp_accept_sec_context_upcall() does \u0026res.options.data[0].value, a NULL+small-offset load that faults on the unmapped zero page. No kernel memory is returned to the attacker; unlike a UAF, freed object contents are never read.\\nI:N - The faulting access is a pure NULL-pointer dereference with no kernel write. The put_group_info() UAF described in the fix is only latent: the unpatched free_creds path kfree()s the svc_cred wrapper without touching cr_group_info, so the dangling pointer is not used.\\nA:H - The NULL dereference oopses the nfsd (or lockd) thread and panics the host where panic_on_oops is set, which is typical on NAS/appliance NFS servers. The same error path also leaks the kvmalloc-backed group_info, and the crash can be repeated to take down SUNRPC service threads.\"}]}], \"affected\": [{\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"5e6013ae2c8d420faea553d363935f65badd32c3\", \"lessThan\": \"8c56a46db3b7523f13e167c3e2c6e3c47a87dcb3\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"3cfcfc102a5e57b021b786a755a38935e357797d\", \"lessThan\": \"fb30241f7ccace372ee83017891549f23a715581\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"3cfcfc102a5e57b021b786a755a38935e357797d\", \"lessThan\": \"3ff45361e9469e85c0f86b8e7b82c63e50bab8ef\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"3cfcfc102a5e57b021b786a755a38935e357797d\", \"lessThan\": \"f85a83774d7f4e2ac71c0c384df0dfb6f7d0179a\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"3cfcfc102a5e57b021b786a755a38935e357797d\", \"lessThan\": \"5e9a94539b1ec17a89177d952badfd0d844d694a\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"b97c37978ca825557d331c9012e0c1ddc0e42364\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"bfa9d86d39a0fe4685f90c3529aa9bd62a9d97a8\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"bb336cd8d5ecb69c430ebe3e7bcff68471d93fa8\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"dd292e884c649f9b1c18af0ec75ca90b390cd044\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"934212a623cbab851848b6de377eb476718c3e4c\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"9806c2393cd2ab0a8e7bb9ffae02ce20e3112ec4\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"996997d1fb2126feda550d6adcedcbd94911fc69\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"6.6.23\", \"lessThan\": \"6.6.160\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"4.19.311\", \"lessThan\": \"4.20\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"5.4.273\", \"lessThan\": \"5.5\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"5.10.214\", \"lessThan\": \"5.11\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"5.15.153\", \"lessThan\": \"5.16\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"6.1.83\", \"lessThan\": \"6.2\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"6.7.11\", \"lessThan\": \"6.8\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"6.8.2\", \"lessThan\": \"6.9\", \"versionType\": \"semver\"}], \"programFiles\": [\"net/sunrpc/auth_gss/gss_rpc_xdr.c\"], \"defaultStatus\": \"unaffected\"}, {\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"6.9\"}, {\"status\": \"unaffected\", \"version\": \"0\", \"lessThan\": \"6.9\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"6.6.160\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.6.*\"}, {\"status\": \"unaffected\", \"version\": \"6.12.111\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.12.*\"}, {\"status\": \"unaffected\", \"version\": \"6.18.51\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.18.*\"}, {\"status\": \"unaffected\", \"version\": \"7.2.4\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"7.2.*\"}, {\"status\": \"unaffected\", \"version\": \"7.3\", \"versionType\": \"original_commit_for_fix\", \"lessThanOrEqual\": \"*\"}], \"programFiles\": [\"net/sunrpc/auth_gss/gss_rpc_xdr.c\"], \"defaultStatus\": \"affected\"}], \"references\": [{\"url\": \"https://git.kernel.org/stable/c/8c56a46db3b7523f13e167c3e2c6e3c47a87dcb3\"}, {\"url\": \"https://git.kernel.org/stable/c/fb30241f7ccace372ee83017891549f23a715581\"}, {\"url\": \"https://git.kernel.org/stable/c/3ff45361e9469e85c0f86b8e7b82c63e50bab8ef\"}, {\"url\": \"https://git.kernel.org/stable/c/f85a83774d7f4e2ac71c0c384df0dfb6f7d0179a\"}, {\"url\": \"https://git.kernel.org/stable/c/5e9a94539b1ec17a89177d952badfd0d844d694a\"}], \"x_generator\": {\"engine\": \"bippy-1.2.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"In the Linux kernel, the following vulnerability has been resolved:\\n\\nSUNRPC: fix gssx_dec_option_array error path bugs\\n\\nFour coupled defects in the gssx XDR option-array decoder make the\\nerror paths unsafe: a NULL deref in the caller, a refcount leak on\\nthe decoded group_info, and a latent use-after-free that the leak\\nfix would otherwise expose.\\n\\ngssx_dec_option_array() sets oa-\u003ecount = 1 before allocating\\noa-\u003edata.  If that allocation fails, -ENOMEM is returned with\\noa-\u003ecount == 1 and oa-\u003edata == NULL.  All other error paths jump\\nto free_oa: which frees oa-\u003edata and NULLs it but also leaves\\noa-\u003ecount == 1.  The caller trusts the count:\\n\\n    gssp_accept_sec_context_upcall()\\n      gssx_dec_accept_sec_context()\\n        gssx_dec_option_array()        /* fails, count=1 data=NULL */\\n      data = res.options.data[0].value /* NULL deref */\\n\\nIndependently, free_creds: releases the partially decoded svc_cred\\nwith a bare kfree(creds).  gssx_dec_linux_creds() installs a\\ngroups_alloc() result into creds-\u003ecr_group_info; that object is\\nkvmalloc-backed and refcounted, and only put_group_info() reaches\\nkvfree().  A plain kfree(creds) drops the wrapper and leaks the\\ngroup_info allocation.\\n\\nThe natural fix for the leak is to call free_svc_cred(creds) before\\nkfree(creds), but free_svc_cred() invokes put_group_info() on\\ncreds-\u003ecr_group_info unconditionally when non-NULL.  The existing\\nout_free_groups: path in gssx_dec_linux_creds() already called\\ngroups_free() on that pointer without clearing it, so once\\nfree_svc_cred() is wired in, the subsequent put_group_info() would\\ntouch freed memory.\\n\\nFix all four together:\\n\\n  - Move the oa-\u003ecount = 1 assignment below the oa-\u003edata allocation\\n    so it is never set when oa-\u003edata is NULL.\\n  - Reset oa-\u003ecount to 0 at free_oa: so count and data stay\\n    coherent and the caller sees an empty option array.\\n  - Call free_svc_cred(creds) before kfree(creds) at free_creds:\\n    so the refcounted cr_group_info is released.  free_svc_cred()\\n    either NULL-guards each field explicitly (cr_group_info has\\n    an if() check) or delegates to a helper that is NULL-safe\\n    itself (kfree for the string fields, gss_mech_put() which\\n    guards with if(gm) at gss_mech_switch.c:342), so it is safe\\n    to call on a partially decoded svc_cred where only\\n    cr_uid/cr_gid/cr_group_info have been written and everything\\n    else is zero from kzalloc.\\n  - In gssx_dec_linux_creds()\u0027s out_free_groups: path, release\\n    cr_group_info with put_group_info() rather than groups_free()\\n    so the teardown matches free_svc_cred()\u0027s refcount-aware path,\\n    and clear the pointer so a later free_svc_cred() on the same\\n    creds does not release it a second time.\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.6.160\", \"versionStartIncluding\": \"6.6.23\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.12.111\", \"versionStartIncluding\": \"6.9\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.18.51\", \"versionStartIncluding\": \"6.9\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"7.2.4\", \"versionStartIncluding\": \"6.9\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"7.3\", \"versionStartIncluding\": \"6.9\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionStartIncluding\": \"4.19.311\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionStartIncluding\": \"5.4.273\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionStartIncluding\": \"5.10.214\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionStartIncluding\": \"5.15.153\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionStartIncluding\": \"6.1.83\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionStartIncluding\": \"6.7.11\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionStartIncluding\": \"6.8.2\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2026-10-21T12:47:49.203Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-89544\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-10-21T12:47:49.203Z\", \"dateReserved\": \"2026-09-11T19:38:34.722Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2026-09-11T19:44:20.424Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


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