CVE-2026-31718 (GCVE-0-2026-31718)

Vulnerability from cvelistv5 – Published: 2026-05-01 13:56 – Updated: 2026-08-05 12:24
VLAI
Title
ksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger When a durable file handle survives session disconnect (TCP close without SMB2_LOGOFF), session_fd_check() sets fp->conn = NULL to preserve the handle for later reconnection. However, it did not clean up the byte-range locks on fp->lock_list. Later, when the durable scavenger thread times out and calls __ksmbd_close_fd(NULL, fp), the lock cleanup loop did: spin_lock(&fp->conn->llist_lock); This caused a slab use-after-free because fp->conn was NULL and the original connection object had already been freed by ksmbd_tcp_disconnect(). The root cause is asymmetric cleanup: lock entries (smb_lock->clist) were left dangling on the freed conn->lock_list while fp->conn was nulled out. To fix this issue properly, we need to handle the lifetime of smb_lock->clist across three paths: - Safely skip clist deletion when list is empty and fp->conn is NULL. - Remove the lock from the old connection's lock_list in session_fd_check() - Re-add the lock to the new connection's lock_list in ksmbd_reopen_durable_fd().
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 8df4bcdb0a4232192b2445256c39b787d58ef14d , < 0000a7780e0e446a28a273572f6ea8f7f582f694 (git)
Affected: c8efcc786146a951091588e5fa7e3c754850cb3c , < e33c65f011980b4ad4abfd93585ec2079856368f (git)
Affected: c8efcc786146a951091588e5fa7e3c754850cb3c , < 3d6682726c2d3a46d31dae88b8166786b09b03ad (git)
Affected: c8efcc786146a951091588e5fa7e3c754850cb3c , < b34fc42cfe922e551f7a27d3ac3bb016e41d7dd9 (git)
Affected: c8efcc786146a951091588e5fa7e3c754850cb3c , < 235e32320a470fcd3998fb3774f2290a0eb302a1 (git)
Affected: 6.6.32 , < 6.6.140 (semver)
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Linux Linux Affected: 6.9
Unaffected: 0 , < 6.9 (semver)
Unaffected: 6.6.140 , ≤ 6.6.* (semver)
Unaffected: 6.12.84 , ≤ 6.12.* (semver)
Unaffected: 6.18.25 , ≤ 6.18.* (semver)
Unaffected: 7.0.2 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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          }
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      "cve": "CVE-2026-31718",
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      "source": "Red Hat CSAF VEX",
      "status": "final",
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      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31718.json",
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      "product_status:recommended": "4",
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      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-31718.json",
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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.

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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.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.