Vulnerability-Lookup

FKIE_CVE-2026-31610

Vulnerability from fkie_nvd - Published: 2026-04-24 15:16 - Updated: 2026-04-29 16:51

Severity

5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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.

References

URL	Tags
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/269c800a7a7e363459291885b35f7bc72e231ed6	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/6c8c44e6553b9f072f62d9875e567766eb293162	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/745a535461bbb90a56d9357573c9f97a5c12abe1	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/ad0057fb91218914d6c98268718ceb9d59b388e1	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/dd53414e301beb915fe672dc4c4a51bafb917604	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/dd577cb55588ec3fbc66af3621280306601c4192	Patch

Impacted products

Vendor	Product	Version
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*

JSON

To clipboard

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      "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": "2026-04-29T16:51:02.850",
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          "availabilityImpact": "HIGH",
          "baseScore": 5.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
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      "source": "nvd@nist.gov",
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  ]
}

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

Vulnerability from cvelistv5 – Published: 2026-04-24 14:42 – Updated: 2026-05-11 22:12

Title

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

Summary

Severity

No CVSS data available.

Assigner

Linux

References

6 references

URL	Tags
https://git.kernel.org/stable/c/745a535461bbb90a5…
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…
https://git.kernel.org/stable/c/ad0057fb91218914d…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: fad4161b5cd01a24202234976ebbb133f7adc0b5 , < 745a535461bbb90a56d9357573c9f97a5c12abe1 (git) Affected: fad4161b5cd01a24202234976ebbb133f7adc0b5 , < dd577cb55588ec3fbc66af3621280306601c4192 (git) Affected: fad4161b5cd01a24202234976ebbb133f7adc0b5 , < dd53414e301beb915fe672dc4c4a51bafb917604 (git) Affected: fad4161b5cd01a24202234976ebbb133f7adc0b5 , < 269c800a7a7e363459291885b35f7bc72e231ed6 (git) Affected: fad4161b5cd01a24202234976ebbb133f7adc0b5 , < 6c8c44e6553b9f072f62d9875e567766eb293162 (git) Affected: fad4161b5cd01a24202234976ebbb133f7adc0b5 , < ad0057fb91218914d6c98268718ceb9d59b388e1 (git)
Linux	Linux	Affected: 5.15 Unaffected: 0 , < 5.15 (semver) Unaffected: 6.6.136 , ≤ 6.6.* (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) Unaffected: 7.1-rc1 , ≤ * (original_commit_for_fix)

Show details on NVD website

JSON

To clipboard

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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.

Action not permitted

FKIE_CVE-2026-31610

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

Tags

Sightings

Nomenclature