CVE-2026-97556 — smb: client: avoid leaking refcount when cifs_sb_tlink() fails
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.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 0.2% (30-day exploitation probability)+1
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Linux Linux).
- No fix documented in the sources: reduce exposure and monitor the vendor advisory.
- Search available logs for exploit probes, errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Linux | Linux |
≥ 5ee28bcfbaacf289eb25c662a2862542ea6ce6a7 and < 55c5f095d4df14271b238f826e1392fda7b6e60e≥ e8f5f849ffce24490eb9449e98312b66c0dba76f and < e9c5bcc88b8337157e480c85a6d2f326bc265012≥ e8f5f849ffce24490eb9449e98312b66c0dba76f and < 9ec991e148368e3207e98134c509a625097f7693≥ e8f5f849ffce24490eb9449e98312b66c0dba76f and < dd03fd658ea59821505e0e643b6b7cbdf51c4e1d≥ e8f5f849ffce24490eb9449e98312b66c0dba76f and < 1d1b0f1d812a4011a57bc6c70492c34a2e46c6dd≥ e8f5f849ffce24490eb9449e98312b66c0dba76f and < 23b26f4408ac3f35a482d2e5cf6fc865d4201b71version b99f490ea87ebcca3a429fd8837067feb56a4c7cversion 6b67a6d2e50634fe127e656147c81915955e9f5e and 4 more≥ 6.1.47 and < 6.1.189≥ 5.15.128 and < 5.16≥ 6.4.12 and < 6.5version 6.5 |
Vulnerable | CVE Program (cve.org) e CISA ADP |
EPSS over time FIRST
Oct 15, 2026 → Oct 16, 2026 · 2 reading(s) · max 0.21%
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Not enough vector or weakness data: use the affected application’s logs as a starting point.
Timeline
What happened to this CVE, newest first.
- 2026
- Record published
- Affected products added · linux/linux
- Source status changed · → Received
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× Official description updated · Oct 15, 2026 – Oct 15, 2026
References
6 on the record
- git.kernel.org/stable/c/1d1b0f1d812a4011a57bc6c70492c34a2e46c6dd
- git.kernel.org/stable/c/23b26f4408ac3f35a482d2e5cf6fc865d4201b71
- git.kernel.org/stable/c/9ec991e148368e3207e98134c509a625097f7693
- git.kernel.org/stable/c/55c5f095d4df14271b238f826e1392fda7b6e60e
- git.kernel.org/stable/c/e9c5bcc88b8337157e480c85a6d2f326bc265012
- git.kernel.org/stable/c/dd03fd658ea59821505e0e643b6b7cbdf51c4e1d
Elsewhere on this site
Related CVEs (same products)
- Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 2d
- Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 2d
- Unknown CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 3d
- Unknown CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 3d
- Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 3d
- Unknown CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 3d
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No CVSS score published by NVD, the CNA, CISA or GitHub so far.
- No fixed version, patch or mitigation documented.
- No CISA SSVC assessment.
- No CWE classification.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-97556 is "smb: client: avoid leaking refcount when cifs_sb_tlink() fails", rated Unknown. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. EPSS 0.21% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
Comments
Moderated technical discussion. Read the community guidelines.
No comments yet.
Sign in or create an account to comment and suggest corrections.