Vulnerability-Lookup

GHSA-G5HW-V48Q-45PV

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:

ksmbd: fix mechToken leak when SPNEGO decode fails after token alloc

The kernel ASN.1 BER decoder calls action callbacks incrementally as it walks the input. When ksmbd_decode_negTokenInit() reaches the mechToken [2] OCTET STRING element, ksmbd_neg_token_alloc() allocates conn->mechToken immediately via kmemdup_nul(). If a later element in the same blob is malformed, then the decoder will return nonzero after the allocation is already live. This could happen if mechListMIC [3] overrunse the enclosing SEQUENCE.

decode_negotiation_token() then sets conn->use_spnego = false because both the negTokenInit and negTokenTarg grammars failed. The cleanup at the bottom of smb2_sess_setup() is gated on use_spnego:

if (conn->use_spnego && conn->mechToken) {
    kfree(conn->mechToken);
    conn->mechToken = NULL;
}

so the kfree is skipped, causing the mechToken to never be freed.

This codepath is reachable pre-authentication, so untrusted clients can cause slow memory leaks on a server without even being properly authenticated.

Fix this up by not checking check for use_spnego, as it's not required, so the memory will always be properly freed. At the same time, always free the memory in ksmbd_conn_free() incase some other failure path forgot to free it.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-31610"
  ],
  "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\nksmbd: fix mechToken leak when SPNEGO decode fails after token alloc\n\nThe kernel ASN.1 BER decoder calls action callbacks incrementally as it\nwalks the input.  When ksmbd_decode_negTokenInit() reaches the mechToken\n[2] OCTET STRING element, ksmbd_neg_token_alloc() allocates\nconn-\u003emechToken immediately via kmemdup_nul().  If a later element in\nthe same blob is malformed, then the decoder will return nonzero after\nthe allocation is already live.  This could happen if mechListMIC [3]\noverrunse the enclosing SEQUENCE.\n\ndecode_negotiation_token() then sets conn-\u003euse_spnego = false because\nboth the negTokenInit and negTokenTarg grammars failed.  The cleanup at\nthe bottom of smb2_sess_setup() is gated on use_spnego:\n\n\tif (conn-\u003euse_spnego \u0026\u0026 conn-\u003emechToken) {\n\t\tkfree(conn-\u003emechToken);\n\t\tconn-\u003emechToken = NULL;\n\t}\n\nso the kfree is skipped, causing the mechToken to never be freed.\n\nThis codepath is reachable pre-authentication, so untrusted clients can\ncause slow memory leaks on a server without even being properly\nauthenticated.\n\nFix this up by not checking check for use_spnego, as it\u0027s not required,\nso the memory will always be properly freed.  At the same time, always\nfree the memory in ksmbd_conn_free() incase some other failure path\nforgot to free it.",
  "id": "GHSA-g5hw-v48q-45pv",
  "modified": "2026-04-24T15:32:35Z",
  "published": "2026-04-24T15:32:35Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31610"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/269c800a7a7e363459291885b35f7bc72e231ed6"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6c8c44e6553b9f072f62d9875e567766eb293162"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/dd53414e301beb915fe672dc4c4a51bafb917604"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/dd577cb55588ec3fbc66af3621280306601c4192"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-31610 (GCVE-0-2026-31610)

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

Title

ksmbd: fix mechToken leak when SPNEGO decode fails after token alloc

Summary

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix mechToken leak when SPNEGO decode fails after token alloc The kernel ASN.1 BER decoder calls action callbacks incrementally as it walks the input. When ksmbd_decode_negTokenInit() reaches the mechToken [2] OCTET STRING element, ksmbd_neg_token_alloc() allocates conn->mechToken immediately via kmemdup_nul(). If a later element in the same blob is malformed, then the decoder will return nonzero after the allocation is already live. This could happen if mechListMIC [3] overrunse the enclosing SEQUENCE. decode_negotiation_token() then sets conn->use_spnego = false because both the negTokenInit and negTokenTarg grammars failed. The cleanup at the bottom of smb2_sess_setup() is gated on use_spnego: if (conn->use_spnego && conn->mechToken) { kfree(conn->mechToken); conn->mechToken = NULL; } so the kfree is skipped, causing the mechToken to never be freed. This codepath is reachable pre-authentication, so untrusted clients can cause slow memory leaks on a server without even being properly authenticated. Fix this up by not checking check for use_spnego, as it's not required, so the memory will always be properly freed. At the same time, always free the memory in ksmbd_conn_free() incase some other failure path forgot to free it.

Severity ?

No CVSS data available.

Assigner

Linux

References

URL

Tags

	https://git.kernel.org/stable/c/dd577cb55588ec3fb…
	https://git.kernel.org/stable/c/dd53414e301beb915…
	https://git.kernel.org/stable/c/269c800a7a7e36345…
	https://git.kernel.org/stable/c/6c8c44e6553b9f072…

Impacted products

Vendor

Product

Version

Linux

Affected: fad4161b5cd01a24202234976ebbb133f7adc0b5 , < dd577cb55588ec3fbc66af3621280306601c4192 (git)
Affected: fad4161b5cd01a24202234976ebbb133f7adc0b5 , < dd53414e301beb915fe672dc4c4a51bafb917604 (git)
Affected: fad4161b5cd01a24202234976ebbb133f7adc0b5 , < 269c800a7a7e363459291885b35f7bc72e231ed6 (git)
Affected: fad4161b5cd01a24202234976ebbb133f7adc0b5 , < 6c8c44e6553b9f072f62d9875e567766eb293162 (git)

Linux

Affected: 5.15
Unaffected: 0 , < 5.15 (semver)
Unaffected: 6.12.83 , ≤ 6.12.* (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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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/connection.c",
            "fs/smb/server/smb2pdu.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "dd577cb55588ec3fbc66af3621280306601c4192",
              "status": "affected",
              "version": "fad4161b5cd01a24202234976ebbb133f7adc0b5",
              "versionType": "git"
            },
            {
              "lessThan": "dd53414e301beb915fe672dc4c4a51bafb917604",
              "status": "affected",
              "version": "fad4161b5cd01a24202234976ebbb133f7adc0b5",
              "versionType": "git"
            },
            {
              "lessThan": "269c800a7a7e363459291885b35f7bc72e231ed6",
              "status": "affected",
              "version": "fad4161b5cd01a24202234976ebbb133f7adc0b5",
              "versionType": "git"
            },
            {
              "lessThan": "6c8c44e6553b9f072f62d9875e567766eb293162",
              "status": "affected",
              "version": "fad4161b5cd01a24202234976ebbb133f7adc0b5",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/connection.c",
            "fs/smb/server/smb2pdu.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.15"
            },
            {
              "lessThan": "5.15",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.83",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.24",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.19.*",
              "status": "unaffected",
              "version": "6.19.14",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.1",
              "versionType": "semver"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.83",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.24",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.19.14",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0.1",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix mechToken leak when SPNEGO decode fails after token alloc\n\nThe kernel ASN.1 BER decoder calls action callbacks incrementally as it\nwalks the input.  When ksmbd_decode_negTokenInit() reaches the mechToken\n[2] OCTET STRING element, ksmbd_neg_token_alloc() allocates\nconn-\u003emechToken immediately via kmemdup_nul().  If a later element in\nthe same blob is malformed, then the decoder will return nonzero after\nthe allocation is already live.  This could happen if mechListMIC [3]\noverrunse the enclosing SEQUENCE.\n\ndecode_negotiation_token() then sets conn-\u003euse_spnego = false because\nboth the negTokenInit and negTokenTarg grammars failed.  The cleanup at\nthe bottom of smb2_sess_setup() is gated on use_spnego:\n\n\tif (conn-\u003euse_spnego \u0026\u0026 conn-\u003emechToken) {\n\t\tkfree(conn-\u003emechToken);\n\t\tconn-\u003emechToken = NULL;\n\t}\n\nso the kfree is skipped, causing the mechToken to never be freed.\n\nThis codepath is reachable pre-authentication, so untrusted clients can\ncause slow memory leaks on a server without even being properly\nauthenticated.\n\nFix this up by not checking check for use_spnego, as it\u0027s not required,\nso the memory will always be properly freed.  At the same time, always\nfree the memory in ksmbd_conn_free() incase some other failure path\nforgot to free it."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-04-25T05:48:17.235Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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          "url": "https://git.kernel.org/stable/c/dd577cb55588ec3fbc66af3621280306601c4192"
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        {
          "url": "https://git.kernel.org/stable/c/269c800a7a7e363459291885b35f7bc72e231ed6"
        },
        {
          "url": "https://git.kernel.org/stable/c/6c8c44e6553b9f072f62d9875e567766eb293162"
        }
      ],
      "title": "ksmbd: fix mechToken leak when SPNEGO decode fails after token alloc",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31610",
    "datePublished": "2026-04-24T14:42:31.471Z",
    "dateReserved": "2026-03-09T15:48:24.122Z",
    "dateUpdated": "2026-04-25T05:48:17.235Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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

GHSA-G5HW-V48Q-45PV

CVE-2026-31610 (GCVE-0-2026-31610)

Tags

Sightings

Nomenclature