CVE-2026-721709p: skip nlink update in cacheless mode to fix WARN_ON
- 7.8HighCVSS base score
- 0.17%Exploitation in 30 daysEPSS · top 94% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
In the Linux kernel, the following vulnerability has been resolved: 9p: skip nlink update in cacheless mode to fix WARN_ON v9fs_dec_count() unconditionally calls drop_nlink() on regular files, even when the inode's nlink is already zero. In cacheless mode the client refetches inode metadata from the server (the source of truth) on every operation, so by the time v9fs_remove() returns, the locally cached nlink may already reflect the post-unlink value: 1. Client initiates unlink, server processes it and sets nlink to 0 2. Client refetches inode metadata (nlink=0) before unlink returns 3. Client's v9fs_remove() completes successfully 4. Client calls v9fs_dec_count() which calls drop_nlink() on nlink=0 This race is easily triggered under heavy unlink workloads, such as stress-ng's unlink stressor, producing the following warning: WARNING: fs/inode.c:417 at drop_nlink+0x4c/0xc8 Call trace: drop_nlink+0x4c/0xc8 v9fs_remove+0x1e0/0x250 [9p] v9fs_vfs_unlink+0x20/0x38 [9p] vfs_unlink+0x13c/0x258 ... In cacheless mode the server is authoritative and the inode is on its way out, so locally adjusting nlink buys nothing. Skip v9fs_dec_count() entirely when neither CACHE_META nor CACHE_LOOSE is set, which both avoids the warning and removes a class of nlink races (two concurrent unlinkers observing nlink > 0 and both calling drop_nlink()) that an nlink == 0 guard alone would only narrow rather than close.
Timeline
ID reserved
By Linux
- 6 days later
· 6 days later
Published
- 2 months later
· 2 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| LinuxCNA (assigner) | 3.1 | High7.8 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
| NVDNVD · Received | 3.1 | High7.8 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 0.17% · top 94% of all CVEs (13 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.8.
Affected products
- affected ac89b2ef9b55924bcf922251f043ba73a32d05bb – < 6086469f7d469549bfd070348b717a6e43736200
- affected ac89b2ef9b55924bcf922251f043ba73a32d05bb – < ab257019cb72f467b55c95384d99c94e3908b928
- affected ac89b2ef9b55924bcf922251f043ba73a32d05bb – < 4ec4ebe40c82cb4c60756732f6593055d010c59c
- affected ac89b2ef9b55924bcf922251f043ba73a32d05bb – < a5a682b016ef5b5384e28f6d652d47a8f8e73d37
- affected ac89b2ef9b55924bcf922251f043ba73a32d05bb – < de79c3f3643841b8659a71958df7cf2a66bfd409
- affected ac89b2ef9b55924bcf922251f043ba73a32d05bb – < 8d610017c992de705b304d3d727a6e3a86af6149
- affected ac89b2ef9b55924bcf922251f043ba73a32d05bb – < 8faccac11e1369adddf5d80f4a45af93f13b2e1a
- affected ac89b2ef9b55924bcf922251f043ba73a32d05bb – < 574aa0b4799470ac814479f1138d19efe6262255
- affected 4.17
- unaffected < 4.17
- unaffected 5.10.266 – ≤ 5.10.*
- unaffected 5.15.217 – ≤ 5.15.*
- unaffected 6.1.184 – ≤ 6.1.*
- unaffected 6.6.145 – ≤ 6.6.*
- unaffected 6.12.97 – ≤ 6.12.*
- unaffected 6.18.40 – ≤ 6.18.*
- unaffected 7.1.5 – ≤ 7.1.*
- unaffected 7.2 – ≤ *
References
References8
- https://git.kernel.org/stable/c/6086469f7d469549bfd070348b717a6e43736200 (opens in a new tab)
- https://git.kernel.org/stable/c/ab257019cb72f467b55c95384d99c94e3908b928 (opens in a new tab)
- https://git.kernel.org/stable/c/4ec4ebe40c82cb4c60756732f6593055d010c59c (opens in a new tab)
- https://git.kernel.org/stable/c/a5a682b016ef5b5384e28f6d652d47a8f8e73d37 (opens in a new tab)
- https://git.kernel.org/stable/c/de79c3f3643841b8659a71958df7cf2a66bfd409 (opens in a new tab)
- https://git.kernel.org/stable/c/8d610017c992de705b304d3d727a6e3a86af6149 (opens in a new tab)
- https://git.kernel.org/stable/c/8faccac11e1369adddf5d80f4a45af93f13b2e1a (opens in a new tab)
- https://git.kernel.org/stable/c/574aa0b4799470ac814479f1138d19efe6262255 (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-58928 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-72170)Record last updated .