nfsd: fix XDR length calculation in nfsd4_ff_encode_layoutget
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA.
Summary
In the Linux kernel, the following vulnerability has been resolved: nfsd: fix XDR length calculation in nfsd4_ff_encode_layoutget The XDR buffer size calculation in nfsd4_ff_encode_layoutget() has multiple errors that can result in either an out-of-bounds write or leaking uninitialized kernel memory to the client: - fh_len doesn't account for XDR padding on the file handle data - uid and gid lengths use "8 + len" but xdr_encode_opaque() actually writes "4 + xdr_align_size(len)" bytes - ds_len omits the flags and stats_collect_hint fields (8 bytes), while len's header constant overestimates by 8 bytes -- these partially cancel but leave a net mismatch The worst case occurs with short strings (e.g. uid=0, gid=0 with an odd-sized file handle), where the function writes up to 5 bytes past the reserved XDR buffer. Conversely, when string lengths happen to be 4-byte aligned, the reservation is too large and stale buffer content is sent to the client. Fix this by breaking out every encoded field explicitly in the ds_len calculation, using xdr_align_size() for all variable-length opaque fields, and correcting the header constants.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
Remediation
- Fix · CNA Linux (Linux) Fixed in 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109, 6.18.50, 7.2.4, 7.3
Vendor assessments
Red Hat
Red Hat rating: Important. Red Hat's page for this CVE →
Not affected: 7 products
- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8
- Red Hat Enterprise Linux 9
- Red Hat OpenShift Container Platform 4
- Red Hat OpenShift Container Platform 5
Timeline
- 2026-10-02 Threatist record created from CVE-2026-89674
- 2026-10-03 Alias added: GHSA-qhmp-vm7x-v422
- 2026-10-05 EPSS moved to the below the 50th percentile
- 2026-10-16 Affected versions changed · Red Hat
- 2026-10-16 CVSS score changed · Red Hat
- 2026-10-19 Fix available: Linux/[email protected] · CNA
- 2026-10-31 Affected versions changed · Red Hat
References
Other 8
- https://git.kernel.org/stable/c/3a7fd224df0fbb42167eb1b77be45d72fe0b1098
- https://git.kernel.org/stable/c/29e4478e2ed5a227e8f0c33cacb91bf227cedd47
- https://git.kernel.org/stable/c/65a72b721943618eeb3a41c8b36e915591f3f83f
- https://git.kernel.org/stable/c/bee826c00ac900473f91306f1f3e5a5a81fd4a74
- https://git.kernel.org/stable/c/e7d9d23ecd9172f05b09bb678ff22db8e361c428
- https://git.kernel.org/stable/c/0380129b1373c437eb35401a174671c8888f4b80
- https://git.kernel.org/stable/c/c81cef6a805dec266c10fc4f83c93d6fcf1a2b43
- https://git.kernel.org/stable/c/f9868174af49d207fbaf0c5e055d088a983684af
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Sources
- CVE-2026-89674 · CVE Program
- CVE-2026-89674 · NVD
- FIRST EPSS
- GHSA-qhmp-vm7x-v422 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-89674 · Red Hat security data · CC BY 4.0
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