nfsd: release path refs on follow_down() error
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 7 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat.
Summary
In the Linux kernel, the following vulnerability has been resolved: nfsd: release path refs on follow_down() error nfsd_cross_mnt() initializes a local struct path with mntget() and dget() before calling follow_down(). On a negative return the error arm jumps to out without releasing those references: err = follow_down(&path, follow_flags); if (err < 0) goto out; follow_down() never drops the caller's entry-time refs on any error sub-case; for example a pre-cross d_manage() failure leaves path untouched, so the mntget()/dget() taken on entry survive the call. Every other early-exit arm in nfsd_cross_mnt() (other-namespace return, IS_ERR(exp2), and the success tail after the swap) already calls path_put(&path); the err < 0 arm is the lone omission. The leak inflates mnt_count and d_count on each failed cross-mount, blocking umount and pinning dentries against the shrinker, and is reachable by any authenticated NFS client through nfsd_lookup_dentry or the NFSv4 READDIR encode path. Fix by calling path_put(&path) before the goto out in the err < 0 arm so the entry-time refs are released on all follow_down() error returns.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Linux | Linux | 2.6.38 and later | 5.10.273, 5.15.224, 6.1.191, 6.6.157, 6.12.109, 6.18.50, 7.2.4, 7.3 | Patch available | CNA |
- Linux VendorLinux Affected 2.6.38 and later Fixed in 5.10.273, 5.15.224, 6.1.191, 6.6.157, 6.12.109, 6.18.50, 7.2.4, 7.3 Patch available CNA
Remediation
- Fix · CNA Linux (Linux) Fixed in 5.10.273, 5.15.224, 6.1.191, 6.6.157, 6.12.109, 6.18.50, 7.2.4, 7.3
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 10 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 7 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Container Platform 5 | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-02 Threatist record created from CVE-2026-89707
- 2026-10-03 Alias added: GHSA-qv85-292c-84hh
- 2026-10-18 CISA SSVC decision points changed
- 2026-10-18 Priority changed: LOW → MEDIUM
- 2026-10-19 Fix available: Linux/[email protected] · CNA
- 2026-10-21 Affected versions changed · Red Hat
- 2026-10-21 CVSS score changed · Red Hat
- 2026-10-30 Fix available: Linux/Linux@18847cbf5900f5c6c55bef5a6f7a34a1918d1181, Linux/[email protected], Linux/[email protected] +3 · CNA
- 2026-10-30 3 new references · CNA
- 2026-10-30 Affected versions changed · Red Hat
- 2026-10-31 EPSS moved to the 50th–90th percentile
References
Other 8
- https://git.kernel.org/stable/c/bdf5a0f88d21239d8f9f7519b87359ba95fd045c
- https://git.kernel.org/stable/c/18847cbf5900f5c6c55bef5a6f7a34a1918d1181
- https://git.kernel.org/stable/c/e301c5cdb0dc2c4aeffc0c055ea15615d9c51fdc
- https://git.kernel.org/stable/c/085cfde7c2186acaad103f02d2c25435ad5224e9
- https://git.kernel.org/stable/c/194316df81263519156ebe714c4a286bee00e5be
- https://git.kernel.org/stable/c/467d56fd3ff57447a790c6dc3ede2d02a947d224
- https://git.kernel.org/stable/c/2bc4343308d85ee4e0dd3877b384306c96f114c2
- https://git.kernel.org/stable/c/6cba08dc1922140d260cfeb30bbda4ee1bf869d8
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Sources
- CVE-2026-89707 · CVE Program
- CVE-2026-89707 · NVD
- FIRST EPSS
- GHSA-qv85-292c-84hh · GitHub Advisory Database · CC BY 4.0
- CVE-2026-89707 · Red Hat security data · CC BY 4.0
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