Vulnerability-Lookup

CVE-2026-31613 (GCVE-0-2026-31613)

Vulnerability from cvelistv5 – Published: 2026-04-24 14:42 – Updated: 2026-04-25 05:48

Title

smb: client: fix OOB reads parsing symlink error response

Summary

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix OOB reads parsing symlink error response When a CREATE returns STATUS_STOPPED_ON_SYMLINK, smb2_check_message() returns success without any length validation, leaving the symlink parsers as the only defense against an untrusted server. symlink_data() walks SMB 3.1.1 error contexts with the loop test "p < end", but reads p->ErrorId at offset 4 and p->ErrorDataLength at offset 0. When the server-controlled ErrorDataLength advances p to within 1-7 bytes of end, the next iteration will read past it. When the matching context is found, sym->SymLinkErrorTag is read at offset 4 from p->ErrorContextData with no check that the symlink header itself fits. smb2_parse_symlink_response() then bounds-checks the substitute name using SMB2_SYMLINK_STRUCT_SIZE as the offset of PathBuffer from iov_base. That value is computed as sizeof(smb2_err_rsp) + sizeof(smb2_symlink_err_rsp), which is correct only when ErrorContextCount == 0. With at least one error context the symlink data sits 8 bytes deeper, and each skipped non-matching context shifts it further by 8 + ALIGN(ErrorDataLength, 8). The check is too short, allowing the substitute name read to run past iov_len. The out-of-bound heap bytes are UTF-16-decoded into the symlink target and returned to userspace via readlink(2). Fix this all up by making the loops test require the full context header to fit, rejecting sym if its header runs past end, and bound the substitute name against the actual position of sym->PathBuffer rather than a fixed offset. Because sub_offs and sub_len are 16bits, the pointer math will not overflow here with the new greater-than.

Severity ?

No CVSS data available.

Assigner

Linux

References

URL

Tags

	https://git.kernel.org/stable/c/e0dd90d14cbbf3181…
	https://git.kernel.org/stable/c/781902e069f4ecb6c…
	https://git.kernel.org/stable/c/a66ef2e7ed837325c…

Impacted products

Vendor

Product

Version

Linux

Affected: 76894f3e2f71177747b8b4763fb180e800279585 , < e0dd90d14cbbf318157ea8e3fb62ee68a28655ed (git)
Affected: 76894f3e2f71177747b8b4763fb180e800279585 , < 781902e069f4ecb6c3b83502f181972c1446110a (git)
Affected: 76894f3e2f71177747b8b4763fb180e800279585 , < a66ef2e7ed837325c5600f8617d5ee0a0a149fdd (git)
Affected: 2d046892a493d9760c35fdaefc3017f27f91b621 (git)

Linux

Affected: 6.1
Unaffected: 0 , < 6.1 (semver)
Unaffected: 6.18.24 , ≤ 6.18.* (semver)
Unaffected: 6.19.14 , ≤ 6.19.* (semver)
Unaffected: 7.0.1 , ≤ 7.0.* (semver)

Show details on NVD website

JSON

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          "programFiles": [
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          "versions": [
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              "version": "6.1"
            },
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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              "version": "6.18.24",
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              "versionType": "semver"
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              "version": "7.0.1",
              "versionType": "semver"
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        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix OOB reads parsing symlink error response\n\nWhen a CREATE returns STATUS_STOPPED_ON_SYMLINK, smb2_check_message()\nreturns success without any length validation, leaving the symlink\nparsers as the only defense against an untrusted server.\n\nsymlink_data() walks SMB 3.1.1 error contexts with the loop test \"p \u003c\nend\", but reads p-\u003eErrorId at offset 4 and p-\u003eErrorDataLength at offset\n0.  When the server-controlled ErrorDataLength advances p to within 1-7\nbytes of end, the next iteration will read past it.  When the matching\ncontext is found, sym-\u003eSymLinkErrorTag is read at offset 4 from\np-\u003eErrorContextData with no check that the symlink header itself fits.\n\nsmb2_parse_symlink_response() then bounds-checks the substitute name\nusing SMB2_SYMLINK_STRUCT_SIZE as the offset of PathBuffer from\niov_base.  That value is computed as sizeof(smb2_err_rsp) +\nsizeof(smb2_symlink_err_rsp), which is correct only when\nErrorContextCount == 0.\n\nWith at least one error context the symlink data sits 8 bytes deeper,\nand each skipped non-matching context shifts it further by 8 +\nALIGN(ErrorDataLength, 8).  The check is too short, allowing the\nsubstitute name read to run past iov_len.  The out-of-bound heap bytes\nare UTF-16-decoded into the symlink target and returned to userspace via\nreadlink(2).\n\nFix this all up by making the loops test require the full context header\nto fit, rejecting sym if its header runs past end, and bound the\nsubstitute name against the actual position of sym-\u003ePathBuffer rather\nthan a fixed offset.\n\nBecause sub_offs and sub_len are 16bits, the pointer math will not\noverflow here with the new greater-than."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-04-25T05:48:20.691Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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        },
        {
          "url": "https://git.kernel.org/stable/c/781902e069f4ecb6c3b83502f181972c1446110a"
        },
        {
          "url": "https://git.kernel.org/stable/c/a66ef2e7ed837325c5600f8617d5ee0a0a149fdd"
        }
      ],
      "title": "smb: client: fix OOB reads parsing symlink error response",
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        "engine": "bippy-1.2.0"
      }
    }
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31613",
    "datePublished": "2026-04-24T14:42:33.453Z",
    "dateReserved": "2026-03-09T15:48:24.123Z",
    "dateUpdated": "2026-04-25T05:48:20.691Z",
    "state": "PUBLISHED"
  },
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  }
}

GHSA-3W37-M4PG-Q585

Vulnerability from github – Published: 2026-04-24 15:32 – Updated: 2026-04-24 15:32

Details

In the Linux kernel, the following vulnerability has been resolved:

smb: client: fix OOB reads parsing symlink error response

When a CREATE returns STATUS_STOPPED_ON_SYMLINK, smb2_check_message() returns success without any length validation, leaving the symlink parsers as the only defense against an untrusted server.

symlink_data() walks SMB 3.1.1 error contexts with the loop test "p < end", but reads p->ErrorId at offset 4 and p->ErrorDataLength at offset 0. When the server-controlled ErrorDataLength advances p to within 1-7 bytes of end, the next iteration will read past it. When the matching context is found, sym->SymLinkErrorTag is read at offset 4 from p->ErrorContextData with no check that the symlink header itself fits.

smb2_parse_symlink_response() then bounds-checks the substitute name using SMB2_SYMLINK_STRUCT_SIZE as the offset of PathBuffer from iov_base. That value is computed as sizeof(smb2_err_rsp) + sizeof(smb2_symlink_err_rsp), which is correct only when ErrorContextCount == 0.

With at least one error context the symlink data sits 8 bytes deeper, and each skipped non-matching context shifts it further by 8 + ALIGN(ErrorDataLength, 8). The check is too short, allowing the substitute name read to run past iov_len. The out-of-bound heap bytes are UTF-16-decoded into the symlink target and returned to userspace via readlink(2).

Fix this all up by making the loops test require the full context header to fit, rejecting sym if its header runs past end, and bound the substitute name against the actual position of sym->PathBuffer rather than a fixed offset.

Because sub_offs and sub_len are 16bits, the pointer math will not overflow here with the new greater-than.

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-31613"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-04-24T15:16:40Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix OOB reads parsing symlink error response\n\nWhen a CREATE returns STATUS_STOPPED_ON_SYMLINK, smb2_check_message()\nreturns success without any length validation, leaving the symlink\nparsers as the only defense against an untrusted server.\n\nsymlink_data() walks SMB 3.1.1 error contexts with the loop test \"p \u003c\nend\", but reads p-\u003eErrorId at offset 4 and p-\u003eErrorDataLength at offset\n0.  When the server-controlled ErrorDataLength advances p to within 1-7\nbytes of end, the next iteration will read past it.  When the matching\ncontext is found, sym-\u003eSymLinkErrorTag is read at offset 4 from\np-\u003eErrorContextData with no check that the symlink header itself fits.\n\nsmb2_parse_symlink_response() then bounds-checks the substitute name\nusing SMB2_SYMLINK_STRUCT_SIZE as the offset of PathBuffer from\niov_base.  That value is computed as sizeof(smb2_err_rsp) +\nsizeof(smb2_symlink_err_rsp), which is correct only when\nErrorContextCount == 0.\n\nWith at least one error context the symlink data sits 8 bytes deeper,\nand each skipped non-matching context shifts it further by 8 +\nALIGN(ErrorDataLength, 8).  The check is too short, allowing the\nsubstitute name read to run past iov_len.  The out-of-bound heap bytes\nare UTF-16-decoded into the symlink target and returned to userspace via\nreadlink(2).\n\nFix this all up by making the loops test require the full context header\nto fit, rejecting sym if its header runs past end, and bound the\nsubstitute name against the actual position of sym-\u003ePathBuffer rather\nthan a fixed offset.\n\nBecause sub_offs and sub_len are 16bits, the pointer math will not\noverflow here with the new greater-than.",
  "id": "GHSA-3w37-m4pg-q585",
  "modified": "2026-04-24T15:32:35Z",
  "published": "2026-04-24T15:32:35Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31613"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/781902e069f4ecb6c3b83502f181972c1446110a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a66ef2e7ed837325c5600f8617d5ee0a0a149fdd"
    },
    {
      "type": "WEB",
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    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

FKIE_CVE-2026-31613

Vulnerability from fkie_nvd - Published: 2026-04-24 15:16 - Updated: 2026-04-24 17:51

Severity ?

Summary

References

	URL	Tags
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/781902e069f4ecb6c3b83502f181972c1446110a
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/a66ef2e7ed837325c5600f8617d5ee0a0a149fdd
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/e0dd90d14cbbf318157ea8e3fb62ee68a28655ed

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix OOB reads parsing symlink error response\n\nWhen a CREATE returns STATUS_STOPPED_ON_SYMLINK, smb2_check_message()\nreturns success without any length validation, leaving the symlink\nparsers as the only defense against an untrusted server.\n\nsymlink_data() walks SMB 3.1.1 error contexts with the loop test \"p \u003c\nend\", but reads p-\u003eErrorId at offset 4 and p-\u003eErrorDataLength at offset\n0.  When the server-controlled ErrorDataLength advances p to within 1-7\nbytes of end, the next iteration will read past it.  When the matching\ncontext is found, sym-\u003eSymLinkErrorTag is read at offset 4 from\np-\u003eErrorContextData with no check that the symlink header itself fits.\n\nsmb2_parse_symlink_response() then bounds-checks the substitute name\nusing SMB2_SYMLINK_STRUCT_SIZE as the offset of PathBuffer from\niov_base.  That value is computed as sizeof(smb2_err_rsp) +\nsizeof(smb2_symlink_err_rsp), which is correct only when\nErrorContextCount == 0.\n\nWith at least one error context the symlink data sits 8 bytes deeper,\nand each skipped non-matching context shifts it further by 8 +\nALIGN(ErrorDataLength, 8).  The check is too short, allowing the\nsubstitute name read to run past iov_len.  The out-of-bound heap bytes\nare UTF-16-decoded into the symlink target and returned to userspace via\nreadlink(2).\n\nFix this all up by making the loops test require the full context header\nto fit, rejecting sym if its header runs past end, and bound the\nsubstitute name against the actual position of sym-\u003ePathBuffer rather\nthan a fixed offset.\n\nBecause sub_offs and sub_len are 16bits, the pointer math will not\noverflow here with the new greater-than."
    }
  ],
  "id": "CVE-2026-31613",
  "lastModified": "2026-04-24T17:51:40.810",
  "metrics": {},
  "published": "2026-04-24T15:16:40.560",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/781902e069f4ecb6c3b83502f181972c1446110a"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a66ef2e7ed837325c5600f8617d5ee0a0a149fdd"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e0dd90d14cbbf318157ea8e3fb62ee68a28655ed"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}

MSRC_CVE-2026-31613

Vulnerability from csaf_microsoft - Published: 2026-04-02 00:00 - Updated: 2026-04-26 01:06

Summary

smb: client: fix OOB reads parsing symlink error response

Notes

Additional Resources: To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle

Disclaimer: The information provided in the Microsoft Knowledge Base is provided \"as is\" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

CVE-2026-31613

References

URL

Sightings

Author	Source	Type	Date

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.

Action not permitted

CVE-2026-31613 (GCVE-0-2026-31613)

GHSA-3W37-M4PG-Q585

FKIE_CVE-2026-31613

MSRC_CVE-2026-31613

Tags

Sightings

Nomenclature