smb: client: avoid leaking refcount when cifs_sb_tlink() fails (CVE-2026-97556) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-97556

smb: client: avoid leaking refcount when cifs_sb_tlink() fails

Answer in brief

CVE-2026-97556 records a Unknown severity vulnerability in smb: client: avoid leaking refcount when cifs_sb_tlink() fails. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 25, 2026Updated Sep 25, 2026Source checked Sep 25, 2026First seen by HOL Sep 25, 2026Material review Sep 25, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Linux/Linuxgeneric	>=e8f5f849ffce24490eb9449e98312b66c0dba76f <9ec991e148368e3207e98134c509a625097f7693 \|\| >=e8f5f849ffce24490eb9449e98312b66c0dba76f <dd03fd658ea59821505e0e643b6b7cbdf51c4e1d \|\| >=e8f5f849ffce24490eb9449e98312b66c0dba76f <1d1b0f1d812a4011a57bc6c70492c34a2e46c6dd \|\| >=e8f5f849ffce24490eb9449e98312b66c0dba76f <23b26f4408ac3f35a482d2e5cf6fc865d4201b71 \|\| b99f490ea87ebcca3a429fd8837067feb56a4c7c \|\| 5ee28bcfbaacf289eb25c662a2862542ea6ce6a7 \|\| 6b67a6d2e50634fe127e656147c81915955e9f5e \|\| >=5.15.128 <5.16 \|\| >=6.1.47 <6.2 \|\| >=6.4.12 <6.5	9ec991e148368e3207e98134c509a625097f7693, dd03fd658ea59821505e0e643b6b7cbdf51c4e1d, 1d1b0f1d812a4011a57bc6c70492c34a2e46c6dd, 23b26f4408ac3f35a482d2e5cf6fc865d4201b71, 5.16, 6.2, 6.5
Linux/Linuxgeneric	6.5	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Linux/Linux, Linux/Linux.
Review the reported fix. Update Linux/Linux to 9ec991e148368e3207e98134c509a625097f7693 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 25, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 25, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 25, 2026

Sources and claim methodology

Upstream source description

In the Linux kernel, the following vulnerability has been resolved: smb: client: avoid leaking refcount when cifs_sb_tlink() fails cifs_oplock_break() takes over the reference that cifs_queue_oplock_break() acquired when it queued the work, and drops it with _cifsFileInfo_put() once the break has been processed. Only in setups with "-o multiuser", cifs_sb_tlink() may fail, at which point cifs_oplock_break() returns without putting the file reference, mirroring the reference leak we already fixed in the companion patch to cifs_queue_oplock_break(). This would trigger a crash due to busy inodes on the next unmount: BUG: Dentry ... still in use (1) [unmount of cifs cifs] VFS: Busy inodes after unmount of cifs (cifs) Drop the reference on that path as well. Doing so before the out label mirrors the normal path, which also puts the reference before cifs_done_oplock_break(). Found by Sashiko code review. The failure path was not exercised at runtime.

Quoted source text, attributed separately from HOL analysis.