CVE-2026-89673: nfsd: fix XDR padding calculation in ff_encode_getdeviceinfo

Severity: unknown
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-11 · updated 2026-10-24

Description

In the Linux kernel, the following vulnerability has been resolved: nfsd: fix XDR padding calculation in ff_encode_getdeviceinfo nfsd4_ff_encode_getdeviceinfo() computes the da_addr_body reservation as 16 + netid_len + addr_len, but the subsequent xdr_encode_opaque() calls emit 8 + round_up(netid_len, 4) + round_up(addr_len, 4) bytes. The mismatch means the declared da_addr_body length exceeds the actual encoded data by 2-8 bytes on every flexfile GETDEVICEINFO reply, leaking stale reply-page content to the client and mis-aligning the subsequent version list decode. Use xdr_align_size() for each string length to match what xdr_encode_opaque() actually writes.

Affected products

Linux kernel: from 5.10.195 before 5.10.270; from 5.15.132 before 5.15.221; from 6.1.53 before 6.1.188; from 4.14.326 before 4.15; from 4.19.295 before 4.20; from 5.4.257 before 5.5 — fixed in 4.15, 4.20, 5.10.270, 5.15.221, 5.5, 6.1.188

How to fix

Upgrade to a fixed version: Linux kernel 4.15, 4.20, 5.10.270, 5.15.221. Check the vendor advisory for mitigations.

References

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