Vulnerability-Lookup

FKIE_CVE-2026-89550

Vulnerability from fkie_nvd - Published: 2026-09-11 20:19 - Updated: 2026-09-14 13:19

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: svcauth_gss: enforce krb5 token minimum length svcauth_gss_unwrap_priv() validates only an upper bound on the wire-supplied opaque length before handing the buffer to gss_unwrap(): if (len > xdr_stream_remaining(xdr)) goto unwrap_failed; offset = xdr_stream_pos(xdr); ... maj_stat = gss_unwrap(ctx, offset, offset + len, buf); The wire value `len` flows unchanged as the upper bound into the krb5 unwrap path, so a len in [0, 16] passes this check and is handed to gss_unwrap(). For a krb5 v2 context that lands in gss_krb5_unwrap_v2(), which reads the 16-byte RFC 4121 token header fields at ptr+4 and ptr+6 and then calls rotate_left() before any integrity check. With a sub-header length the header reads run past the token, and _rotate_left()'s `shift %= buf->len` path can divide by zero when buf->len has been driven to zero by the truncated token. A header-only token (len == 16) is equally invalid: with a non-zero RRC field and the opaque blob ending at the XDR buffer boundary, rotate_left() builds a zero-length subbuffer, reaching the same division. Reject the token at the server entry point before it reaches the krb5 unwrap core. A valid sealed RFC 4121 token must contain the 16-byte header plus at least some encrypted payload. Fix by adding a minimum-length check immediately after the existing upper-bound check: if (len <= GSS_KRB5_TOK_HDR_LEN) goto unwrap_failed;

References

	URL	Tags
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/0ea5b0c7f212c2772d32c2b88287b89a9cdf6edd
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/2eed1e6a976a44015c3ee78841fe336796e2b21c
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/a919c5c88769cf8fb3ec071e6078d830bf512489
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/dd6afc6cab8c5d387d1ed2f069562ef7bdadd651
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/de942dd8c2c8358bcad04ce44271954c48924423

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/sunrpc/auth_gss/svcauth_gss.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "0ea5b0c7f212c2772d32c2b88287b89a9cdf6edd",
              "status": "affected",
              "version": "7c9fdcfb1b64c47ed618c103b617af3f86e1239c",
              "versionType": "git"
            },
            {
              "lessThan": "dd6afc6cab8c5d387d1ed2f069562ef7bdadd651",
              "status": "affected",
              "version": "7c9fdcfb1b64c47ed618c103b617af3f86e1239c",
              "versionType": "git"
            },
            {
              "lessThan": "de942dd8c2c8358bcad04ce44271954c48924423",
              "status": "affected",
              "version": "7c9fdcfb1b64c47ed618c103b617af3f86e1239c",
              "versionType": "git"
            },
            {
              "lessThan": "2eed1e6a976a44015c3ee78841fe336796e2b21c",
              "status": "affected",
              "version": "7c9fdcfb1b64c47ed618c103b617af3f86e1239c",
              "versionType": "git"
            },
            {
              "lessThan": "a919c5c88769cf8fb3ec071e6078d830bf512489",
              "status": "affected",
              "version": "7c9fdcfb1b64c47ed618c103b617af3f86e1239c",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/sunrpc/auth_gss/svcauth_gss.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.18"
            },
            {
              "lessThan": "2.6.18",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.157",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.109",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: svcauth_gss: enforce krb5 token minimum length\n\nsvcauth_gss_unwrap_priv() validates only an upper bound on the\nwire-supplied opaque length before handing the buffer to\ngss_unwrap():\n\n    if (len \u003e xdr_stream_remaining(xdr))\n            goto unwrap_failed;\n    offset = xdr_stream_pos(xdr);\n    ...\n    maj_stat = gss_unwrap(ctx, offset, offset + len, buf);\n\nThe wire value `len` flows unchanged as the upper bound into the\nkrb5 unwrap path, so a len in [0, 16] passes this check and is\nhanded to gss_unwrap(). For a krb5 v2 context that lands in\ngss_krb5_unwrap_v2(), which reads the 16-byte RFC 4121 token\nheader fields at ptr+4 and ptr+6 and then calls rotate_left()\nbefore any integrity check. With a sub-header length the header\nreads run past the token, and _rotate_left()\u0027s `shift %= buf-\u003elen`\npath can divide by zero when buf-\u003elen has been driven to zero by\nthe truncated token. A header-only token (len == 16) is equally\ninvalid: with a non-zero RRC field and the opaque blob ending at\nthe XDR buffer boundary, rotate_left() builds a zero-length\nsubbuffer, reaching the same division.\n\nReject the token at the server entry point before it reaches the\nkrb5 unwrap core. A valid sealed RFC 4121 token must contain\nthe 16-byte header plus at least some encrypted payload.\n\nFix by adding a minimum-length check immediately after the\nexisting upper-bound check:\n\n    if (len \u003c= GSS_KRB5_TOK_HDR_LEN)\n            goto unwrap_failed;"
    }
  ],
  "id": "CVE-2026-89550",
  "lastModified": "2026-09-14T13:19:10.017",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-09-11T20:19:38.500",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/0ea5b0c7f212c2772d32c2b88287b89a9cdf6edd"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/2eed1e6a976a44015c3ee78841fe336796e2b21c"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a919c5c88769cf8fb3ec071e6078d830bf512489"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/dd6afc6cab8c5d387d1ed2f069562ef7bdadd651"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/de942dd8c2c8358bcad04ce44271954c48924423"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}

CVE-2026-89550 (GCVE-0-2026-89550)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:44 – Updated: 2026-09-14 12:00

Title

SUNRPC: svcauth_gss: enforce krb5 token minimum length

Summary

Severity

9.8 (Critical)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Assigner

Linux mitre root

References

5 references

URL	Tags
https://git.kernel.org/stable/c/0ea5b0c7f212c2772…
https://git.kernel.org/stable/c/dd6afc6cab8c5d387…
https://git.kernel.org/stable/c/de942dd8c2c8358bc…
https://git.kernel.org/stable/c/2eed1e6a976a44015…
https://git.kernel.org/stable/c/a919c5c88769cf8fb…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 7c9fdcfb1b64c47ed618c103b617af3f86e1239c , < 0ea5b0c7f212c2772d32c2b88287b89a9cdf6edd (git) Affected: 7c9fdcfb1b64c47ed618c103b617af3f86e1239c , < dd6afc6cab8c5d387d1ed2f069562ef7bdadd651 (git) Affected: 7c9fdcfb1b64c47ed618c103b617af3f86e1239c , < de942dd8c2c8358bcad04ce44271954c48924423 (git) Affected: 7c9fdcfb1b64c47ed618c103b617af3f86e1239c , < 2eed1e6a976a44015c3ee78841fe336796e2b21c (git) Affected: 7c9fdcfb1b64c47ed618c103b617af3f86e1239c , < a919c5c88769cf8fb3ec071e6078d830bf512489 (git)
Linux	Linux	Affected: 2.6.18 Unaffected: 0 , < 2.6.18 (semver) Unaffected: 6.6.157 , ≤ 6.6.* (semver) Unaffected: 6.12.109 , ≤ 6.12.* (semver) Unaffected: 6.18.50 , ≤ 6.18.* (semver) Unaffected: 7.2.4 , ≤ 7.2.* (semver) Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/sunrpc/auth_gss/svcauth_gss.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "0ea5b0c7f212c2772d32c2b88287b89a9cdf6edd",
              "status": "affected",
              "version": "7c9fdcfb1b64c47ed618c103b617af3f86e1239c",
              "versionType": "git"
            },
            {
              "lessThan": "dd6afc6cab8c5d387d1ed2f069562ef7bdadd651",
              "status": "affected",
              "version": "7c9fdcfb1b64c47ed618c103b617af3f86e1239c",
              "versionType": "git"
            },
            {
              "lessThan": "de942dd8c2c8358bcad04ce44271954c48924423",
              "status": "affected",
              "version": "7c9fdcfb1b64c47ed618c103b617af3f86e1239c",
              "versionType": "git"
            },
            {
              "lessThan": "2eed1e6a976a44015c3ee78841fe336796e2b21c",
              "status": "affected",
              "version": "7c9fdcfb1b64c47ed618c103b617af3f86e1239c",
              "versionType": "git"
            },
            {
              "lessThan": "a919c5c88769cf8fb3ec071e6078d830bf512489",
              "status": "affected",
              "version": "7c9fdcfb1b64c47ed618c103b617af3f86e1239c",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/sunrpc/auth_gss/svcauth_gss.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.18"
            },
            {
              "lessThan": "2.6.18",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.157",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.109",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.157",
                  "versionStartIncluding": "2.6.18",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.109",
                  "versionStartIncluding": "2.6.18",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.50",
                  "versionStartIncluding": "2.6.18",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.4",
                  "versionStartIncluding": "2.6.18",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3-rc1",
                  "versionStartIncluding": "2.6.18",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: svcauth_gss: enforce krb5 token minimum length\n\nsvcauth_gss_unwrap_priv() validates only an upper bound on the\nwire-supplied opaque length before handing the buffer to\ngss_unwrap():\n\n    if (len \u003e xdr_stream_remaining(xdr))\n            goto unwrap_failed;\n    offset = xdr_stream_pos(xdr);\n    ...\n    maj_stat = gss_unwrap(ctx, offset, offset + len, buf);\n\nThe wire value `len` flows unchanged as the upper bound into the\nkrb5 unwrap path, so a len in [0, 16] passes this check and is\nhanded to gss_unwrap(). For a krb5 v2 context that lands in\ngss_krb5_unwrap_v2(), which reads the 16-byte RFC 4121 token\nheader fields at ptr+4 and ptr+6 and then calls rotate_left()\nbefore any integrity check. With a sub-header length the header\nreads run past the token, and _rotate_left()\u0027s `shift %= buf-\u003elen`\npath can divide by zero when buf-\u003elen has been driven to zero by\nthe truncated token. A header-only token (len == 16) is equally\ninvalid: with a non-zero RRC field and the opaque blob ending at\nthe XDR buffer boundary, rotate_left() builds a zero-length\nsubbuffer, reaching the same division.\n\nReject the token at the server entry point before it reaches the\nkrb5 unwrap core. A valid sealed RFC 4121 token must contain\nthe 16-byte header plus at least some encrypted payload.\n\nFix by adding a minimum-length check immediately after the\nexisting upper-bound check:\n\n    if (len \u003c= GSS_KRB5_TOK_HDR_LEN)\n            goto unwrap_failed;"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "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"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - svcauth_gss_unwrap_priv() is reached from in-kernel nfsd over TCP/2049 (svc_authenticate \u2192 svcauth_gss_accept) and from the NFSv4.0 RPC_AUTH_GSS callback service, so a remote RPCSEC_GSS peer delivers the short krb5 wrap token over the network.\nAC:L - A single RPCSEC_GSS DATA Call with gc_svc=PRIVACY and opaque length in [0, 16] plus a non-zero RRC in the cleartext RFC 4121 header deterministically hits gss_krb5_unwrap_v2() rotate_left() u32 wrap and shift%=0; no race or attacker-uncontrollable layout is required.\nPR:N - A malicious NFS server that already shares a krb5p GSS context can send a crafted NFSv4.0 GSS callback into the client\u0027s svcauth_gss_unwrap_priv() with no account or capability on the victim. That peer path is the highest-severity reachability.\nUI:N - nfsd unwraps the Call in the service thread with no local user action. On the client, the NFSv4.0 GSS callback path runs from the callback service thread once an NFS/RPCSEC_GSS mount exists; no additional mount, click, or open is required at attack time.\nS:U - The out-of-bounds accesses, divide-by-zero, and underflowed memmove corrupt host kernel SUNRPC/GSS state on the machine processing the RPC. This is ordinary same-host kernel impact, not a VM escape, IOMMU bypass, or other changed-scope boundary.\nC:H - Short tokens make gss_krb5_unwrap_v2() read EC/RRC past the token, and the dead BUG_ON lets unsigned movelen underflow into a ~UINT_MAX-byte memmove that copies kernel memory beyond the receive head; that unbounded read is C:H per kernel CNA memory-corruption guidance.\nI:H - The same underflowed memmove() writes near 4GiB through the RPC receive head, an out-of-bounds write exploitable for control-flow hijack. rotate_left() also ignores xdr_buf_subsegment() failure after u32 wrap and then writes through a subbuf whose length has wrapped.\nA:H - _rotate_left() does shift %= buf-\u003elen on a zero-length subbuffer (header-only token at the XDR boundary), a divide-by-zero oops/panic; the UINT_MAX memmove and wrapped-length rotate loop hang or oops nfsd/callback threads, and the attacker can repeat the RPC to deny service."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-14T12:00:53.633Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/0ea5b0c7f212c2772d32c2b88287b89a9cdf6edd"
        },
        {
          "url": "https://git.kernel.org/stable/c/dd6afc6cab8c5d387d1ed2f069562ef7bdadd651"
        },
        {
          "url": "https://git.kernel.org/stable/c/de942dd8c2c8358bcad04ce44271954c48924423"
        },
        {
          "url": "https://git.kernel.org/stable/c/2eed1e6a976a44015c3ee78841fe336796e2b21c"
        },
        {
          "url": "https://git.kernel.org/stable/c/a919c5c88769cf8fb3ec071e6078d830bf512489"
        }
      ],
      "title": "SUNRPC: svcauth_gss: enforce krb5 token minimum length",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89550",
    "datePublished": "2026-09-11T19:44:24.572Z",
    "dateReserved": "2026-09-11T19:38:34.723Z",
    "dateUpdated": "2026-09-14T12:00:53.633Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.