Vulnerability-Lookup

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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          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/connection.c",
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              "versionType": "semver"
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              "version": "6.19.14",
              "versionType": "semver"
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              "version": "7.0.1",
              "versionType": "semver"
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                },
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      "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"
      },
      "references": [
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        },
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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"
  },
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  }
}

MSRC_CVE-2026-31610

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

Summary

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

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-2026-31610

References

URL

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.

Show details on source website

JSON

To clipboard

{
  "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"
    },
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    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

FKIE_CVE-2026-31610

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/269c800a7a7e363459291885b35f7bc72e231ed6
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/6c8c44e6553b9f072f62d9875e567766eb293162
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/dd53414e301beb915fe672dc4c4a51bafb917604
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/dd577cb55588ec3fbc66af3621280306601c4192

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "cveTags": [],
  "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."
    }
  ],
  "id": "CVE-2026-31610",
  "lastModified": "2026-04-24T17:51:40.810",
  "metrics": {},
  "published": "2026-04-24T15:16:40.257",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/269c800a7a7e363459291885b35f7bc72e231ed6"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/6c8c44e6553b9f072f62d9875e567766eb293162"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/dd53414e301beb915fe672dc4c4a51bafb917604"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/dd577cb55588ec3fbc66af3621280306601c4192"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}

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

MSRC_CVE-2026-31610

GHSA-G5HW-V48Q-45PV

FKIE_CVE-2026-31610

Tags

Sightings

Nomenclature