# CVE-2026-89674

## Summary

- **CVE ID:** CVE-2026-89674
- **Severity:** CRITICAL
- **CVSS Score:** 9.8 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H)
- **CWE:** N/A
- **Published:** Sep 11, 2026
- **Last Modified:** Sep 14, 2026

## Description

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.

## Affected Products

- Linux — Linux (9b9960a0ca4773e21c4b153ed355583946346b25)
- Linux — Linux (4.8)
- Linux — Linux (0)
- Linux — Linux (6.12.109)
- Linux — Linux (6.18.50)
- Linux — Linux (7.2.4)
- Linux — Linux (7.3-rc1)
- Linux — Linux (5.10.270)
- Linux — Linux (5.15.221)
- Linux — Linux (6.1.188)
- Linux — Linux (6.6.157)

## References

- [CNA](https://git.kernel.org/stable/c/e7d9d23ecd9172f05b09bb678ff22db8e361c428)
- [CNA](https://git.kernel.org/stable/c/0380129b1373c437eb35401a174671c8888f4b80)
- [CNA](https://git.kernel.org/stable/c/c81cef6a805dec266c10fc4f83c93d6fcf1a2b43)
- [CNA](https://git.kernel.org/stable/c/f9868174af49d207fbaf0c5e055d088a983684af)
- [CNA](https://git.kernel.org/stable/c/3a7fd224df0fbb42167eb1b77be45d72fe0b1098)
- [CNA](https://git.kernel.org/stable/c/29e4478e2ed5a227e8f0c33cacb91bf227cedd47)
- [CNA](https://git.kernel.org/stable/c/65a72b721943618eeb3a41c8b36e915591f3f83f)
- [CNA](https://git.kernel.org/stable/c/bee826c00ac900473f91306f1f3e5a5a81fd4a74)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.52%
- **EPSS Percentile:** 43.0

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-17._