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CVE-2026-89674

nfsd: fix XDR length calculation in nfsd4_ff_encode_layoutget

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109, and 2 more
None on Exploit-DB, Metasploit or GitHub

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.

Timeline

  1. CVE published
  2. Record last updated

Affected versions

  • Linux Linux

    From 9b9960a0ca4773e21c4b153ed355583946346b25 · fixed in 3a7fd224df0fbb42167eb1b77be45d72fe0b1098; From 9b9960a0ca4773e21c4b153ed355583946346b25 · fixed in 29e4478e2ed5a227e8f0c33cacb91bf227cedd47; From 9b9960a0ca4773e21c4b153ed355583946346b25 · fixed in 65a72b721943618eeb3a41c8b36e915591f3f83f; From 9b9960a0ca4773e21c4b153ed355583946346b25 · fixed in bee826c00ac900473f91306f1f3e5a5a81fd4a74; From 9b9960a0ca4773e21c4b153ed355583946346b25 · fixed in e7d9d23ecd9172f05b09bb678ff22db8e361c428; From 9b9960a0ca4773e21c4b153ed355583946346b25 · fixed in 0380129b1373c437eb35401a174671c8888f4b80; From 9b9960a0ca4773e21c4b153ed355583946346b25 · fixed in c81cef6a805dec266c10fc4f83c93d6fcf1a2b43; From 9b9960a0ca4773e21c4b153ed355583946346b25 · fixed in f9868174af49d207fbaf0c5e055d088a983684af

  • Linux Linux

    4.8

  • KernelLinux

    From 4.8.0 · fixed in 5.10.270; From 5.11.0 · fixed in 5.15.221; From 5.16.0 · fixed in 6.1.188; From 6.2.0 · fixed in 6.6.157; From 6.7.0 · fixed in 6.12.109; From 6.13.0 · fixed in 6.18.50; From 6.19.0 · fixed in 7.2.4

References 8

git.kernel.org