CVE-2026-31402

Description

In the Linux kernel, the following vulnerability has been resolved:nfsd: fix heap overflow in NFSv4.0 LOCK replay cacheThe NFSv4.0 replay cache uses a fixed 112-byte inline buffer(rp_ibuf[NFSD4_REPLAY_ISIZE]) to store encoded operation responses.This size was calculated based on OPEN responses and does not accountfor LOCK denied responses, which include the conflicting lock owner asa variable-length field up to 1024 bytes (NFS4_OPAQUE_LIMIT).When a LOCK operation is denied due to a conflict with an existing lockthat has a large owner, nfsd4_encode_operation() copies the full encodedresponse into the undersized replay buffer via read_bytes_from_xdr_buf()with no bounds check. This results in a slab-out-of-bounds write of upto 944 bytes past the end of the buffer, corrupting adjacent heap memory.This can be triggered remotely by an unauthenticated attacker with twocooperating NFSv4.0 clients: one sets a lock with a large owner string,then the other requests a conflicting lock to provoke the denial.We could fix this by increasing NFSD4_REPLAY_ISIZE to allow for a fullopaque, but that would increase the size of every stateowner, when mostlockowners are not that large.Instead, fix this by checking the encoded response length againstNFSD4_REPLAY_ISIZE before copying into the replay buffer. If theresponse is too large, set rp_buflen to 0 to skip caching the replaypayload. The status is still cached, and the client already received thecorrect response on the original request.

Risk Information

Associated Vulnerability

Patch Details

References

https://nvd.nist.gov/vuln/detail/CVE-2023-1234
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-1234