CVE-2026-89541 (GCVE-0-2026-89541)
Vulnerability from cvelistv5
Published
2026-09-11 19:44
Modified
2026-10-19 08:48
Severity ?
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: SUNRPC: harden gss_unwrap_resp_priv length checks gss_unwrap_resp_priv() validates the RPCSEC_GSS opaque length with offset = (u8 *)(p) - (u8 *)head->iov_base; if (offset + opaque_len > rcv_buf->len) goto unwrap_failed; maj_stat = gss_unwrap(ctx->gc_gss_ctx, offset, offset + opaque_len, rcv_buf); Both operands are u32 and the sum is computed in u32. A reply with opaque_len near 0xffffffff makes offset + opaque_len wrap to a small value that is below rcv_buf->len, so the bound check passes and gss_unwrap() is called with end < begin. The check also lacks a lower bound, so any opaque_len in [0, GSS_KRB5_TOK_HDR_LEN) is accepted and forwarded to gss_krb5_unwrap_v2(), whose pre-decrypt header reads at ptr+4 and ptr+6 then run past the token. A krb5p NFS server returning a crafted RPCSEC_GSS reply can drive the client into out-of-bounds reads in gss_krb5_unwrap_v2() and the rotate_left() loop that follows. Fix by replacing the single combined check with three guards that are safe in u32 arithmetic and that enforce the RFC 4121 minimum outer token length: if (offset > rcv_buf->len) goto unwrap_failed; if (opaque_len > rcv_buf->len - offset) goto unwrap_failed; if (opaque_len < GSS_KRB5_TOK_HDR_LEN) goto unwrap_failed; The first guard makes the subtraction in the second guard unconditionally safe; offset is derived from a successful xdr_inline_decode() in the head kvec, so in practice it already satisfies the bound. The floor mirrors the server-side check added in commit 5b757c2e57a5 ("SUNRPC: svcauth_gss: enforce krb5 token minimum length").
References
Impacted products
Vendor Product Version
Linux Linux Version: 2d2da60c63b67174add32f06e8d54c3a0c5cd9cf
Version: 2d2da60c63b67174add32f06e8d54c3a0c5cd9cf
Version: 2d2da60c63b67174add32f06e8d54c3a0c5cd9cf
Version: 2d2da60c63b67174add32f06e8d54c3a0c5cd9cf
Version: 2d2da60c63b67174add32f06e8d54c3a0c5cd9cf
Version: 2d2da60c63b67174add32f06e8d54c3a0c5cd9cf
Version: 2d2da60c63b67174add32f06e8d54c3a0c5cd9cf
Version: 2d2da60c63b67174add32f06e8d54c3a0c5cd9cf
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: harden gss_unwrap_resp_priv length checks\n\ngss_unwrap_resp_priv() validates the RPCSEC_GSS opaque length with\n\n    offset = (u8 *)(p) - (u8 *)head-\u003eiov_base;\n    if (offset + opaque_len \u003e rcv_buf-\u003elen)\n            goto unwrap_failed;\n    maj_stat = gss_unwrap(ctx-\u003egc_gss_ctx, offset,\n                          offset + opaque_len, rcv_buf);\n\nBoth operands are u32 and the sum is computed in u32. A reply with\nopaque_len near 0xffffffff makes offset + opaque_len wrap to a small\nvalue that is below rcv_buf-\u003elen, so the bound check passes and\ngss_unwrap() is called with end \u003c begin. The check also lacks a\nlower bound, so any opaque_len in [0, GSS_KRB5_TOK_HDR_LEN) is\naccepted and forwarded to gss_krb5_unwrap_v2(), whose pre-decrypt\nheader reads at ptr+4 and ptr+6 then run past the token.\n\nA krb5p NFS server returning a crafted RPCSEC_GSS reply can drive\nthe client into out-of-bounds reads in gss_krb5_unwrap_v2() and the\nrotate_left() loop that follows.\n\nFix by replacing the single combined check with three guards that\nare safe in u32 arithmetic and that enforce the RFC 4121 minimum\nouter token length:\n\n    if (offset \u003e rcv_buf-\u003elen)\n            goto unwrap_failed;\n    if (opaque_len \u003e rcv_buf-\u003elen - offset)\n            goto unwrap_failed;\n    if (opaque_len \u003c GSS_KRB5_TOK_HDR_LEN)\n            goto unwrap_failed;\n\nThe first guard makes the subtraction in the second guard\nunconditionally safe; offset is derived from a successful\nxdr_inline_decode() in the head kvec, so in practice it already\nsatisfies the bound. The floor mirrors the server-side check added\nin commit 5b757c2e57a5 (\"SUNRPC: svcauth_gss: enforce krb5 token\nminimum length\")."
        }
      ],
      "metrics": [
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            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
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              "lang": "en",
              "value": "AV:N - gss_unwrap_resp_priv() runs in the Linux NFS/SUNRPC client while decoding RPCSEC_GSS privacy (krb5p) replies; a malicious or compromised NFS server supplies the crafted opaque_len and wrap token over the existing TCP/UDP/RDMA RPC connection.\nAC:L - The attacker fully controls the reply, including opaque_len and the cleartext RFC 4121 header, and a single response can make offset+opaque_len wrap in u32 or fall below GSS_KRB5_TOK_HDR_LEN; no race or layout beyond the attacker\u2019s control is required.\nPR:N - The attacker is the remote RPC/NFS peer that already holds the GSS session keys needed to pass gss_validate(); no local account, user namespace, or capability on the victim client is required.\nUI:N - Once a krb5p NFS mount or other SUNRPC GSS-privacy client is already in use, normal client RPCs elicit replies the attacker can craft; no extra victim action is needed at attack time.\nS:U - Out-of-bounds reads, rotate/decrypt memory corruption, and crashes stay inside the victim kernel\u2019s SUNRPC client and do not cross a VM, IOMMU, or other security-authority boundary.\nC:H - A short or wrapped opaque_len makes gss_krb5_unwrap_v2() read past the token at ptr+4/ptr+6 and feeds rotate_left()/decrypt with wrapped lengths, disclosing adjacent kernel memory; unwrap cleanup can also memmove nearly UINT_MAX bytes.\nI:H - The same wrapped lengths drive rotate_left() writes, CBC/AEAD decrypt over an unbounded xdr subsegment (xdr_buf_subsegment\u2019s error is ignored), and gss_krb5_unwrap_v2()\u2019s unsigned movelen underflow into a near-4GiB memmove, enabling kernel memory corruption.\nA:H - rotate_left() can divide-by-zero on a zero-length subbuffer, spin in a multi-gigabyte kernel loop on a wrapped subsegment, or oops/panic on the huge memmove or out-of-bounds header access."
            }
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        }
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      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:48:32.929Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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      "references": [
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          "url": "https://git.kernel.org/stable/c/3691c4b3488d8ca046b9941e5be30c626dbbbb50"
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          "url": "https://git.kernel.org/stable/c/89a15a50f84d32d4b99db86f957427fcbe20a99a"
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    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89541",
    "datePublished": "2026-09-11T19:44:18.188Z",
    "dateReserved": "2026-09-11T19:38:34.721Z",
    "dateUpdated": "2026-10-19T08:48:32.929Z",
    "state": "PUBLISHED"
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The attacker fully controls the reply, including opaque_len and the cleartext RFC 4121 header, and a single response can make offset+opaque_len wrap in u32 or fall below GSS_KRB5_TOK_HDR_LEN; no race or layout beyond the attacker\\u2019s control is required.\\nPR:N - The attacker is the remote RPC/NFS peer that already holds the GSS session keys needed to pass gss_validate(); no local account, user namespace, or capability on the victim client is required.\\nUI:N - Once a krb5p NFS mount or other SUNRPC GSS-privacy client is already in use, normal client RPCs elicit replies the attacker can craft; no extra victim action is needed at attack time.\\nS:U - Out-of-bounds reads, rotate/decrypt memory corruption, and crashes stay inside the victim kernel\\u2019s SUNRPC client and do not cross a VM, IOMMU, or other security-authority boundary.\\nC:H - A short or wrapped opaque_len makes gss_krb5_unwrap_v2() read past the token at ptr+4/ptr+6 and feeds rotate_left()/decrypt with wrapped lengths, disclosing adjacent kernel memory; unwrap cleanup can also memmove nearly UINT_MAX bytes.\\nI:H - The same wrapped lengths drive rotate_left() writes, CBC/AEAD decrypt over an unbounded xdr subsegment (xdr_buf_subsegment\\u2019s error is ignored), and gss_krb5_unwrap_v2()\\u2019s unsigned movelen underflow into a near-4GiB memmove, enabling kernel memory corruption.\\nA:H - rotate_left() can divide-by-zero on a zero-length subbuffer, spin in a multi-gigabyte kernel loop on a wrapped subsegment, or oops/panic on the huge memmove or out-of-bounds header access.\"}]}], \"affected\": [{\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"2d2da60c63b67174add32f06e8d54c3a0c5cd9cf\", \"lessThan\": \"3691c4b3488d8ca046b9941e5be30c626dbbbb50\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"2d2da60c63b67174add32f06e8d54c3a0c5cd9cf\", \"lessThan\": \"85fa6b12e8f439739ac36ef2aad925f37c8b976a\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"2d2da60c63b67174add32f06e8d54c3a0c5cd9cf\", \"lessThan\": \"401f6a5b338d05bb1069ad814d9f77e3c367854f\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"2d2da60c63b67174add32f06e8d54c3a0c5cd9cf\", \"lessThan\": \"81fd7654a8429718adfcb2a7e03496077f547ed0\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"2d2da60c63b67174add32f06e8d54c3a0c5cd9cf\", \"lessThan\": \"89a15a50f84d32d4b99db86f957427fcbe20a99a\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"2d2da60c63b67174add32f06e8d54c3a0c5cd9cf\", \"lessThan\": \"ebcbd2523a8524c3d24e111cdbed8e271d910269\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"2d2da60c63b67174add32f06e8d54c3a0c5cd9cf\", \"lessThan\": \"d395c30d570ca6168f0297b191709927d1258273\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"2d2da60c63b67174add32f06e8d54c3a0c5cd9cf\", \"lessThan\": \"87831b92112c81db251d46756d65daa4f91af6a2\", \"versionType\": \"git\"}], \"programFiles\": [\"net/sunrpc/auth_gss/auth_gss.c\"], \"defaultStatus\": \"unaffected\"}, {\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"2.6.15\"}, {\"status\": \"unaffected\", \"version\": \"0\", \"lessThan\": \"2.6.15\", \"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/auth_gss.c\"], \"defaultStatus\": \"affected\"}], \"references\": [{\"url\": \"https://git.kernel.org/stable/c/3691c4b3488d8ca046b9941e5be30c626dbbbb50\"}, {\"url\": \"https://git.kernel.org/stable/c/85fa6b12e8f439739ac36ef2aad925f37c8b976a\"}, {\"url\": \"https://git.kernel.org/stable/c/401f6a5b338d05bb1069ad814d9f77e3c367854f\"}, {\"url\": \"https://git.kernel.org/stable/c/81fd7654a8429718adfcb2a7e03496077f547ed0\"}, {\"url\": \"https://git.kernel.org/stable/c/89a15a50f84d32d4b99db86f957427fcbe20a99a\"}, {\"url\": \"https://git.kernel.org/stable/c/ebcbd2523a8524c3d24e111cdbed8e271d910269\"}, {\"url\": \"https://git.kernel.org/stable/c/d395c30d570ca6168f0297b191709927d1258273\"}, {\"url\": \"https://git.kernel.org/stable/c/87831b92112c81db251d46756d65daa4f91af6a2\"}], \"x_generator\": {\"engine\": \"bippy-1.2.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"In the Linux kernel, the following vulnerability has been resolved:\\n\\nSUNRPC: harden gss_unwrap_resp_priv length checks\\n\\ngss_unwrap_resp_priv() validates the RPCSEC_GSS opaque length with\\n\\n    offset = (u8 *)(p) - (u8 *)head-\u003eiov_base;\\n    if (offset + opaque_len \u003e rcv_buf-\u003elen)\\n            goto unwrap_failed;\\n    maj_stat = gss_unwrap(ctx-\u003egc_gss_ctx, offset,\\n                          offset + opaque_len, rcv_buf);\\n\\nBoth operands are u32 and the sum is computed in u32. A reply with\\nopaque_len near 0xffffffff makes offset + opaque_len wrap to a small\\nvalue that is below rcv_buf-\u003elen, so the bound check passes and\\ngss_unwrap() is called with end \u003c begin. The check also lacks a\\nlower bound, so any opaque_len in [0, GSS_KRB5_TOK_HDR_LEN) is\\naccepted and forwarded to gss_krb5_unwrap_v2(), whose pre-decrypt\\nheader reads at ptr+4 and ptr+6 then run past the token.\\n\\nA krb5p NFS server returning a crafted RPCSEC_GSS reply can drive\\nthe client into out-of-bounds reads in gss_krb5_unwrap_v2() and the\\nrotate_left() loop that follows.\\n\\nFix by replacing the single combined check with three guards that\\nare safe in u32 arithmetic and that enforce the RFC 4121 minimum\\nouter token length:\\n\\n    if (offset \u003e rcv_buf-\u003elen)\\n            goto unwrap_failed;\\n    if (opaque_len \u003e rcv_buf-\u003elen - offset)\\n            goto unwrap_failed;\\n    if (opaque_len \u003c GSS_KRB5_TOK_HDR_LEN)\\n            goto unwrap_failed;\\n\\nThe first guard makes the subtraction in the second guard\\nunconditionally safe; offset is derived from a successful\\nxdr_inline_decode() in the head kvec, so in practice it already\\nsatisfies the bound. The floor mirrors the server-side check added\\nin commit 5b757c2e57a5 (\\\"SUNRPC: svcauth_gss: enforce krb5 token\\nminimum length\\\").\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.270\", \"versionStartIncluding\": \"2.6.15\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.15.221\", \"versionStartIncluding\": \"2.6.15\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.1.188\", \"versionStartIncluding\": \"2.6.15\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.6.157\", \"versionStartIncluding\": \"2.6.15\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.12.109\", \"versionStartIncluding\": \"2.6.15\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.18.50\", \"versionStartIncluding\": \"2.6.15\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"7.2.4\", \"versionStartIncluding\": \"2.6.15\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"7.3\", \"versionStartIncluding\": \"2.6.15\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2026-10-19T08:48:32.929Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-89541\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-10-19T08:48:32.929Z\", \"dateReserved\": \"2026-09-11T19:38:34.721Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2026-09-11T19:44:18.188Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


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