CVE-2026-89695

Status: UPDATED  |  Advisory ID: CVE-2026-89695

Key Details

Affected Products, Subsystems & Sectors

What to Know

In the Linux kernel, the following vulnerability has been resolved:

nfsd: cap decoded POSIX ACL count to bound sort cost

nfsd4_decode_posixacl() reads a u32 entry count off the wire and passes

it straight to posix_acl_alloc() and sort_pacl_range(). The latter is

an O(n^2) bubble sort, so a client-chosen count drives unbounded CPU in

the server's compound processing path.

nfsd4_decode_posixacl()

xdr_stream_decode_u32(&count) /* uncapped u32 */

posix_acl_alloc(count, GFP_KERNEL)

sort_pacl_range(*acl, 0, count - 1) /* O(n^2) bubble sort */

The encoder side in the same file already rejects ACLs whose a_count

exceeds NFS_ACL_MAX_ENTRIES, but the decoder introduced in commit

5fc51dfc2eb1 ("NFSD: Add support for XDR decoding POSIX draft ACLs")

omitted the symmetric check.

Fix by rejecting a wire count greater than NFS_ACL_MAX_ENTRIES with

nfserr_inval, before any allocation, so the sort is bounded by

NFS_ACL_MAX_ENTRIES^2 comparisons.

While we're in here, also fix the nfserr_resource return if

posix_acl_alloc() fails. That's not a legal error code for v4.1+. Change

it to return nfserr_jukebox as that's more appropriate for memory

allocation failures. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References