CVE-2026-89674nfsd: fix XDR length calculation in nfsd4_ff_encode_layoutget
Updated under an hour ago ()
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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.
- CVSS
- 9.8 CRITICAL (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Linux
- NVD analysis
- Received
- Record last updated
- Oct 19, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Linux Linux linux:linux (from the name) | 9b9960a0ca4773e21c4b153ed355583946346b25 builds before 3a7fd224df0fbb42167eb1b77be45d72fe0b1098; from 9b9960a0ca4773e21c4b153ed355583946346b25 before 29e4478e2ed5a227e8f0c33cacb91bf227cedd47; from 9b9960a0ca4773e21c4b153ed355583946346b25 before 65a72b721943618eeb3a41c8b36e915591f3f83f; from 9b9960a0ca4773e21c4b153ed355583946346b25 before bee826c00ac900473f91306f1f3e5a5a81fd4a74; from 9b9960a0ca4773e21c4b153ed355583946346b25 before e7d9d23ecd9172f05b09bb678ff22db8e361c428; from 9b9960a0ca4773e21c4b153ed355583946346b25 before 0380129b1373c437eb35401a174671c8888f4b80; from 9b9960a0ca4773e21c4b153ed355583946346b25 before c81cef6a805dec266c10fc4f83c93d6fcf1a2b43; from 9b9960a0ca4773e21c4b153ed355583946346b25 before f9868174af49d207fbaf0c5e055d088a983684af | CNA record |
References
- 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
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.