CVE-2026-31709 (GCVE-0-2026-31709)

Vulnerability from cvelistv5 – Published: 2026-05-01 13:56 – Updated: 2026-06-09 10:41
VLAI
Title
smb: client: validate the whole DACL before rewriting it in cifsacl
Summary
In the Linux kernel, the following vulnerability has been resolved: smb: client: validate the whole DACL before rewriting it in cifsacl build_sec_desc() and id_mode_to_cifs_acl() derive a DACL pointer from a server-supplied dacloffset and then use the incoming ACL to rebuild the chmod/chown security descriptor. The original fix only checked that the struct smb_acl header fits before reading dacl_ptr->size or dacl_ptr->num_aces. That avoids the immediate header-field OOB read, but the rewrite helpers still walk ACEs based on pdacl->num_aces with no structural validation of the incoming DACL body. A malicious server can return a truncated DACL that still contains a header, claims one or more ACEs, and then drive replace_sids_and_copy_aces() or set_chmod_dacl() past the validated extent while they compare or copy attacker-controlled ACEs. Factor the DACL structural checks into validate_dacl(), extend them to validate each ACE against the DACL bounds, and use the shared validator before the chmod/chown rebuild paths. parse_dacl() reuses the same validator so the read-side parser and write-side rewrite paths agree on what constitutes a well-formed incoming DACL.
Severity
8.8 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 , < 8e47d297e7cf9a6029a0d38e7b22faba7d7aaf12 (git)
Affected: bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 , < d92f3f0b22414e7515696a02224d0af55e3004a3 (git)
Affected: bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 , < ff0ca46b13b9ef6edbcd238a3b6caacfef8ba0e5 (git)
Affected: bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 , < b78db9bddc84136f6a0bb49e8883cf200dfb87a8 (git)
Affected: bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 , < 0a8cf165566ba55a39fd0f4de172119dd646d39a (git)
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Linux Linux Affected: 5.12
Unaffected: 0 , < 5.12 (semver)
Unaffected: 6.6.140 , ≤ 6.6.* (semver)
Unaffected: 6.12.86 , ≤ 6.12.* (semver)
Unaffected: 6.18.35 , ≤ 6.18.* (semver)
Unaffected: 7.0.2 , ≤ 7.0.* (semver)
Unaffected: 7.1-rc1 , ≤ * (original_commit_for_fix)
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}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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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.


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