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CVE-2026-89699: nfsd: validate symlink target length in NFSv4 CREATE

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-11 · updated 2026-10-19

Description

In the Linux kernel, the following vulnerability has been resolved: nfsd: validate symlink target length in NFSv4 CREATE nfsd4_decode_create() accepts an unbounded cr_datalen from the wire for NF4LNK symlink targets, allowing a client to force a kmalloc of up to the maximum RPC payload size (several MiB) per COMPOUND op that persists until compound teardown. The VFS rejects oversized targets with ENAMETOOLONG, but the allocation has already occurred. Reject cr_datalen == 0 early with nfserr_inval and cr_datalen greater than NFS4_MAXPATHLEN (PATH_MAX) with nfserr_nametoolong to bound the allocation.

Affected products

• Linux kernel: 2.6.12 — fixed in 7.3

How to fix

Upgrade to a fixed version: Linux kernel 7.3. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/041f57056e5fb9c80adc088269322d2c61074406
• https://git.kernel.org/stable/c/36011308b3f01ce7dc9954f3cefcbb5291af9f95
• https://git.kernel.org/stable/c/3ef5e7a01a4d74995a65496bc9166d1e980a4355
• https://git.kernel.org/stable/c/45ec115cbfecb4b3cfab7fca6f73d1b60696a25a
• https://git.kernel.org/stable/c/8661d3cb38fd148947e57dbc0871fd4d3fa33bbf
• https://git.kernel.org/stable/c/888dad4b557352cf85be31613407b5ba51ad07d1
• https://git.kernel.org/stable/c/895a485cd3758031ef9993c0d53cf19ce8fb4ccc
• https://git.kernel.org/stable/c/b24843ea3de1676b29902457b38507c95a80649b

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