CVE-2026-89540 (GCVE-0-2026-89540)
Vulnerability from cvelistv5
Published
2026-09-11 19:44
Modified
2026-10-19 08:48
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: sunrpc: init gssp_lock before publishing proc entry create_use_gss_proxy_proc_entry() publishes /proc/net/rpc/use-gss-proxy via proc_create_data() before init_gssp_clnt() runs mutex_init() on sn->gssp_lock. Once the dentry is linked under proc_subdir_lock it is immediately reachable from userspace, so a write that lands in the window drives set_gssp_clnt() into mutex_lock() on a zero-initialized struct mutex. create_use_gss_proxy_proc_entry(net) proc_create_data("use-gss-proxy", ...) /* dentry live */ init_gssp_clnt(sn) mutex_init(&sn->gssp_lock) /* too late */ write_gssp() set_gssp_clnt(net) mutex_lock(&sn->gssp_lock) /* uninitialized */ gssp_rpc_create(...) sn->gssp_clnt = clnt mutex_unlock(&sn->gssp_lock) The window spans only the two statements between proc_create_data() returning and init_gssp_clnt(), so a writer reaches it only if the registering thread is preempted there while another task is already opening the freshly published file. register_pernet_subsys() runs in preemptible context under pernet_ops_rwsem, so that preemption is possible, and the window widens on auth_rpcgss module load, when the proc entry is created for every live net namespace whose tasks are already running. A writer that wins the race locks a zero-filled struct mutex. On CONFIG_DEBUG_MUTEXES the missing magic value trips a "lock used without init" splat; on a production kernel the fast path acquires the lock via CMPXCHG(owner, 0, current). In the latter case a second writer that arrives before init_gssp_clnt() re-zeroes owner can enter set_gssp_clnt() concurrently, shut down the first writer's clnt while it is still in use, and leak the loser's clnt. Fix by initializing sn->gssp_lock in sunrpc_init_net() so its lifetime matches the sunrpc_net it lives in. sn->gssp_clnt is already NULL from the kzalloc that backs net_generic storage, so the lazy helper is no longer needed; drop init_gssp_clnt(), its prototype, and the call from create_use_gss_proxy_proc_entry(). sunrpc.ko is a build-time dependency of auth_rpcgss.ko, so sunrpc_init_net() has always run on every netns before any auth_gss pernet init can publish the proc entry.
References
Impacted products
Vendor Product Version
Linux Linux Version: 030d794bf49855f5e2a9e8dfbfad34211d1eb08b
Version: 030d794bf49855f5e2a9e8dfbfad34211d1eb08b
Version: 030d794bf49855f5e2a9e8dfbfad34211d1eb08b
Version: 030d794bf49855f5e2a9e8dfbfad34211d1eb08b
Version: 030d794bf49855f5e2a9e8dfbfad34211d1eb08b
Version: 030d794bf49855f5e2a9e8dfbfad34211d1eb08b
Version: 030d794bf49855f5e2a9e8dfbfad34211d1eb08b
Version: 030d794bf49855f5e2a9e8dfbfad34211d1eb08b
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsunrpc: init gssp_lock before publishing proc entry\n\ncreate_use_gss_proxy_proc_entry() publishes /proc/net/rpc/use-gss-proxy\nvia proc_create_data() before init_gssp_clnt() runs mutex_init() on\nsn-\u003egssp_lock.  Once the dentry is linked under proc_subdir_lock it is\nimmediately reachable from userspace, so a write that lands in the\nwindow drives set_gssp_clnt() into mutex_lock() on a zero-initialized\nstruct mutex.\n\n    create_use_gss_proxy_proc_entry(net)\n      proc_create_data(\"use-gss-proxy\", ...)   /* dentry live */\n      init_gssp_clnt(sn)\n        mutex_init(\u0026sn-\u003egssp_lock)             /* too late */\n\n    write_gssp()\n      set_gssp_clnt(net)\n        mutex_lock(\u0026sn-\u003egssp_lock)             /* uninitialized */\n        gssp_rpc_create(...)\n        sn-\u003egssp_clnt = clnt\n        mutex_unlock(\u0026sn-\u003egssp_lock)\n\nThe window spans only the two statements between proc_create_data()\nreturning and init_gssp_clnt(), so a writer reaches it only if the\nregistering thread is preempted there while another task is already\nopening the freshly published file.  register_pernet_subsys() runs in\npreemptible context under pernet_ops_rwsem, so that preemption is\npossible, and the window widens on auth_rpcgss module load, when the\nproc entry is created for every live net namespace whose tasks are\nalready running.  A writer that wins the race locks a zero-filled\nstruct mutex.  On CONFIG_DEBUG_MUTEXES the missing magic value trips a\n\"lock used without init\" splat; on a production kernel the fast path\nacquires the lock via CMPXCHG(owner, 0, current).  In the latter case\na second writer that arrives before init_gssp_clnt() re-zeroes owner\ncan enter set_gssp_clnt() concurrently, shut down the first writer\u0027s\nclnt while it is still in use, and leak the loser\u0027s clnt.\n\nFix by initializing sn-\u003egssp_lock in sunrpc_init_net() so its lifetime\nmatches the sunrpc_net it lives in.  sn-\u003egssp_clnt is already NULL from\nthe kzalloc that backs net_generic storage, so the lazy helper is no\nlonger needed; drop init_gssp_clnt(), its prototype, and the call from\ncreate_use_gss_proxy_proc_entry().  sunrpc.ko is a build-time\ndependency of auth_rpcgss.ko, so sunrpc_init_net() has always run on\nevery netns before any auth_gss pernet init can publish the proc\nentry."
        }
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The bug is reached only by write(2) to /proc/net/rpc/use-gss-proxy (write_gssp \u2192 set_gssp_clnt \u2192 mutex_lock(\u0026sn-\u003egssp_lock)); remote NFS/RPC peers never hit that procfs path.\nAC:L - The attacker fully controls writer threads that hammer the proc file, and on auth_rpcgss module load register_pernet_subsys() publishes it for every live netns whose tasks are already running; preemption between proc_create_data() and mutex_init() is possible in that preemptible pernet context, so the race is attacker-driven.\nPR:L - The 0600 use-gss-proxy entry inherits /proc/net ownership from proc_net_ns_init()\u0027s make_kuid(net-\u003euser_ns, 0), so an unprivileged user who unshares user+net namespaces owns the file; write_gssp() has no capable() check.\nUI:N - The attacker creates the namespace and writes \"1\" to the proc file from their own tasks; no victim must mount a filesystem, open a file, or otherwise cooperate.\nS:U - Uninitialized-mutex use and concurrent rpc_clnt teardown corrupt host kernel memory inside the same kernel security authority; this is not a VM escape, IOMMU bypass, or other cross-boundary impact.\nC:H - A writer that wins the race locks a zeroed mutex; mutex_init() can then re-zero owner so a second writer enters set_gssp_clnt() concurrently and rpc_shutdown_client()s a live rpc_clnt, a use-after-free that per kernel guidance yields an arbitrary read primitive.\nI:H - Concurrent set_gssp_clnt() can shut down an in-use rpc_clnt (UAF) while mutex_init() of a held lock corrupts mutex wait-list state, giving heap/lock-structure writes exploitable for control-flow hijack rather than a pure crash.\nA:H - CONFIG_DEBUG_MUTEXES treats the uninitialized lock as a lock-used-without-init splat/oops, and on production kernels the rpc_clnt UAF and corrupted mutex wait lists cause a kernel oops or panic."
            }
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      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:48:31.930Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/159a4fab7170badd6c4a553aef81cac079d6f4ee"
        },
        {
          "url": "https://git.kernel.org/stable/c/b3526ae3351968f6726bcbe25d8d09973ad79109"
        },
        {
          "url": "https://git.kernel.org/stable/c/7f5bcdc8da15077ebe846c2756a5a17741021410"
        },
        {
          "url": "https://git.kernel.org/stable/c/89c8e0733e8c46b7973503f15b1b31a8587d8030"
        },
        {
          "url": "https://git.kernel.org/stable/c/f15b87521168c2a92cb1931f532cba422f856f01"
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          "url": "https://git.kernel.org/stable/c/edeefb111d6181a4aa278f415b005efe284b9489"
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          "url": "https://git.kernel.org/stable/c/3f019571928b269feebcff59926ec13294215e0e"
        },
        {
          "url": "https://git.kernel.org/stable/c/5ce1ed6159731a41fdd0b03eedbed4e147036a5a"
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      "title": "sunrpc: init gssp_lock before publishing proc entry",
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89540",
    "datePublished": "2026-09-11T19:44:17.440Z",
    "dateReserved": "2026-09-11T19:38:34.721Z",
    "dateUpdated": "2026-10-19T08:48:31.930Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
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      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-89540\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"total\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-10-16T19:23:23.496498Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-10-16T19:23:24.509Z\"}}], \"cna\": {\"title\": \"sunrpc: init gssp_lock before publishing proc entry\", \"metrics\": [{\"cvssV3_1\": {\"version\": \"3.1\", \"baseScore\": 7.8, \"baseSeverity\": \"HIGH\", \"vectorString\": \"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"AV:L - The bug is reached only by write(2) to /proc/net/rpc/use-gss-proxy (write_gssp \\u2192 set_gssp_clnt \\u2192 mutex_lock(\u0026sn-\u003egssp_lock)); remote NFS/RPC peers never hit that procfs path.\\nAC:L - The attacker fully controls writer threads that hammer the proc file, and on auth_rpcgss module load register_pernet_subsys() publishes it for every live netns whose tasks are already running; preemption between proc_create_data() and mutex_init() is possible in that preemptible pernet context, so the race is attacker-driven.\\nPR:L - The 0600 use-gss-proxy entry inherits /proc/net ownership from proc_net_ns_init()\u0027s make_kuid(net-\u003euser_ns, 0), so an unprivileged user who unshares user+net namespaces owns the file; write_gssp() has no capable() check.\\nUI:N - The attacker creates the namespace and writes \\\"1\\\" to the proc file from their own tasks; no victim must mount a filesystem, open a file, or otherwise cooperate.\\nS:U - Uninitialized-mutex use and concurrent rpc_clnt teardown corrupt host kernel memory inside the same kernel security authority; this is not a VM escape, IOMMU bypass, or other cross-boundary impact.\\nC:H - A writer that wins the race locks a zeroed mutex; mutex_init() can then re-zero owner so a second writer enters set_gssp_clnt() concurrently and rpc_shutdown_client()s a live rpc_clnt, a use-after-free that per kernel guidance yields an arbitrary read primitive.\\nI:H - Concurrent set_gssp_clnt() can shut down an in-use rpc_clnt (UAF) while mutex_init() of a held lock corrupts mutex wait-list state, giving heap/lock-structure writes exploitable for control-flow hijack rather than a pure crash.\\nA:H - CONFIG_DEBUG_MUTEXES treats the uninitialized lock as a lock-used-without-init splat/oops, and on production kernels the rpc_clnt UAF and corrupted mutex wait lists cause a kernel oops or panic.\"}]}], \"affected\": [{\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"030d794bf49855f5e2a9e8dfbfad34211d1eb08b\", \"lessThan\": \"159a4fab7170badd6c4a553aef81cac079d6f4ee\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"030d794bf49855f5e2a9e8dfbfad34211d1eb08b\", \"lessThan\": \"b3526ae3351968f6726bcbe25d8d09973ad79109\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"030d794bf49855f5e2a9e8dfbfad34211d1eb08b\", \"lessThan\": \"7f5bcdc8da15077ebe846c2756a5a17741021410\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"030d794bf49855f5e2a9e8dfbfad34211d1eb08b\", \"lessThan\": \"89c8e0733e8c46b7973503f15b1b31a8587d8030\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"030d794bf49855f5e2a9e8dfbfad34211d1eb08b\", \"lessThan\": \"f15b87521168c2a92cb1931f532cba422f856f01\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"030d794bf49855f5e2a9e8dfbfad34211d1eb08b\", \"lessThan\": \"edeefb111d6181a4aa278f415b005efe284b9489\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"030d794bf49855f5e2a9e8dfbfad34211d1eb08b\", \"lessThan\": \"3f019571928b269feebcff59926ec13294215e0e\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"030d794bf49855f5e2a9e8dfbfad34211d1eb08b\", \"lessThan\": \"5ce1ed6159731a41fdd0b03eedbed4e147036a5a\", \"versionType\": \"git\"}], \"programFiles\": [\"net/sunrpc/auth_gss/gss_rpc_upcall.c\", \"net/sunrpc/auth_gss/gss_rpc_upcall.h\", \"net/sunrpc/auth_gss/svcauth_gss.c\", \"net/sunrpc/sunrpc_syms.c\"], \"defaultStatus\": \"unaffected\"}, {\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"3.10\"}, {\"status\": \"unaffected\", \"version\": \"0\", \"lessThan\": \"3.10\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"5.10.270\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.10.*\"}, {\"status\": \"unaffected\", \"version\": \"5.15.221\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.15.*\"}, {\"status\": \"unaffected\", \"version\": \"6.1.188\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.1.*\"}, {\"status\": \"unaffected\", \"version\": \"6.6.157\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.6.*\"}, {\"status\": \"unaffected\", \"version\": \"6.12.109\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.12.*\"}, {\"status\": \"unaffected\", \"version\": \"6.18.50\", \"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_upcall.c\", \"net/sunrpc/auth_gss/gss_rpc_upcall.h\", \"net/sunrpc/auth_gss/svcauth_gss.c\", \"net/sunrpc/sunrpc_syms.c\"], \"defaultStatus\": \"affected\"}], \"references\": [{\"url\": \"https://git.kernel.org/stable/c/159a4fab7170badd6c4a553aef81cac079d6f4ee\"}, {\"url\": \"https://git.kernel.org/stable/c/b3526ae3351968f6726bcbe25d8d09973ad79109\"}, {\"url\": \"https://git.kernel.org/stable/c/7f5bcdc8da15077ebe846c2756a5a17741021410\"}, {\"url\": \"https://git.kernel.org/stable/c/89c8e0733e8c46b7973503f15b1b31a8587d8030\"}, {\"url\": \"https://git.kernel.org/stable/c/f15b87521168c2a92cb1931f532cba422f856f01\"}, {\"url\": \"https://git.kernel.org/stable/c/edeefb111d6181a4aa278f415b005efe284b9489\"}, {\"url\": \"https://git.kernel.org/stable/c/3f019571928b269feebcff59926ec13294215e0e\"}, {\"url\": \"https://git.kernel.org/stable/c/5ce1ed6159731a41fdd0b03eedbed4e147036a5a\"}], \"x_generator\": {\"engine\": \"bippy-1.2.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"In the Linux kernel, the following vulnerability has been resolved:\\n\\nsunrpc: init gssp_lock before publishing proc entry\\n\\ncreate_use_gss_proxy_proc_entry() publishes /proc/net/rpc/use-gss-proxy\\nvia proc_create_data() before init_gssp_clnt() runs mutex_init() on\\nsn-\u003egssp_lock.  Once the dentry is linked under proc_subdir_lock it is\\nimmediately reachable from userspace, so a write that lands in the\\nwindow drives set_gssp_clnt() into mutex_lock() on a zero-initialized\\nstruct mutex.\\n\\n    create_use_gss_proxy_proc_entry(net)\\n      proc_create_data(\\\"use-gss-proxy\\\", ...)   /* dentry live */\\n      init_gssp_clnt(sn)\\n        mutex_init(\u0026sn-\u003egssp_lock)             /* too late */\\n\\n    write_gssp()\\n      set_gssp_clnt(net)\\n        mutex_lock(\u0026sn-\u003egssp_lock)             /* uninitialized */\\n        gssp_rpc_create(...)\\n        sn-\u003egssp_clnt = clnt\\n        mutex_unlock(\u0026sn-\u003egssp_lock)\\n\\nThe window spans only the two statements between proc_create_data()\\nreturning and init_gssp_clnt(), so a writer reaches it only if the\\nregistering thread is preempted there while another task is already\\nopening the freshly published file.  register_pernet_subsys() runs in\\npreemptible context under pernet_ops_rwsem, so that preemption is\\npossible, and the window widens on auth_rpcgss module load, when the\\nproc entry is created for every live net namespace whose tasks are\\nalready running.  A writer that wins the race locks a zero-filled\\nstruct mutex.  On CONFIG_DEBUG_MUTEXES the missing magic value trips a\\n\\\"lock used without init\\\" splat; on a production kernel the fast path\\nacquires the lock via CMPXCHG(owner, 0, current).  In the latter case\\na second writer that arrives before init_gssp_clnt() re-zeroes owner\\ncan enter set_gssp_clnt() concurrently, shut down the first writer\u0027s\\nclnt while it is still in use, and leak the loser\u0027s clnt.\\n\\nFix by initializing sn-\u003egssp_lock in sunrpc_init_net() so its lifetime\\nmatches the sunrpc_net it lives in.  sn-\u003egssp_clnt is already NULL from\\nthe kzalloc that backs net_generic storage, so the lazy helper is no\\nlonger needed; drop init_gssp_clnt(), its prototype, and the call from\\ncreate_use_gss_proxy_proc_entry().  sunrpc.ko is a build-time\\ndependency of auth_rpcgss.ko, so sunrpc_init_net() has always run on\\nevery netns before any auth_gss pernet init can publish the proc\\nentry.\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.270\", \"versionStartIncluding\": \"3.10\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.15.221\", \"versionStartIncluding\": \"3.10\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.1.188\", \"versionStartIncluding\": \"3.10\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.6.157\", \"versionStartIncluding\": \"3.10\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.12.109\", \"versionStartIncluding\": \"3.10\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.18.50\", \"versionStartIncluding\": \"3.10\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"7.2.4\", \"versionStartIncluding\": \"3.10\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"7.3\", \"versionStartIncluding\": \"3.10\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2026-10-19T08:48:31.930Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-89540\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-10-19T08:48:31.930Z\", \"dateReserved\": \"2026-09-11T19:38:34.721Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2026-09-11T19:44:17.440Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


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