In the Linux kernel, the following vulnerability has been resolved: nfsd: fix heap overflow in NFSv4.0 LOCK replay cache The 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 account for LOCK denied responses, which include the conflicting lock owner as a variable-length field up to 1024 bytes (NFS4_OPAQUE_LIMIT). When a LOCK operation is denied due to a conflict with an existing lock that has a large owner, nfsd4_encode_operation() copies the full encoded response 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 up to 944 bytes past the end of the buffer, corrupting adjacent heap memory. This can be triggered remotely by an unauthenticated attacker with two cooperating 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 full opaque, but that would increase the size of every stateowner, when most lockowners are not that large. Instead, fix this by checking the encoded response length against NFSD4_REPLAY_ISIZE before copying into the replay buffer. If the response is too large, set rp_buflen to 0 to skip caching the replay payload. The status is still cached, and the client already received the correct response on the original request.
Upstream advisory: https://lore.kernel.org/linux-cve-announce/2026040327-CVE-2026-31402-3e6a@gregkh/T
This issue has been addressed in the following products: Red Hat Enterprise Linux 9.4 Extended Update Support Via RHSA-2026:10108 https://access.redhat.com/errata/RHSA-2026:10108
This issue has been addressed in the following products: Red Hat Enterprise Linux 9.6 Extended Update Support Via RHSA-2026:11313 https://access.redhat.com/errata/RHSA-2026:11313
This issue has been addressed in the following products: Red Hat Enterprise Linux 9 Via RHSA-2026:13565 https://access.redhat.com/errata/RHSA-2026:13565
This issue has been addressed in the following products: Red Hat Enterprise Linux 10 Via RHSA-2026:13566 https://access.redhat.com/errata/RHSA-2026:13566
This issue has been addressed in the following products: Red Hat Enterprise Linux 8 Via RHSA-2026:13578 https://access.redhat.com/errata/RHSA-2026:13578
This issue has been addressed in the following products: Red Hat Enterprise Linux 8 Via RHSA-2026:13577 https://access.redhat.com/errata/RHSA-2026:13577
This issue has been addressed in the following products: Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions Red Hat Enterprise Linux 8.6 Telecommunications Update Service Via RHSA-2026:13664 https://access.redhat.com/errata/RHSA-2026:13664
This issue has been addressed in the following products: Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions Red Hat Enterprise Linux 8.8 Telecommunications Update Service Via RHSA-2026:13681 https://access.redhat.com/errata/RHSA-2026:13681
This issue has been addressed in the following products: Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions Via RHSA-2026:13734 https://access.redhat.com/errata/RHSA-2026:13734
This issue has been addressed in the following products: Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions Via RHSA-2026:13936 https://access.redhat.com/errata/RHSA-2026:13936
This issue has been addressed in the following products: Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions Via RHSA-2026:14137 https://access.redhat.com/errata/RHSA-2026:14137
This issue has been addressed in the following products: Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On Via RHSA-2026:14165 https://access.redhat.com/errata/RHSA-2026:14165
This issue has been addressed in the following products: Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions Via RHSA-2026:14301 https://access.redhat.com/errata/RHSA-2026:14301
This issue has been addressed in the following products: Red Hat Enterprise Linux 6 Extended Lifecycle Support - EXTENSION Via RHSA-2026:14823 https://access.redhat.com/errata/RHSA-2026:14823
This issue has been addressed in the following products: Red Hat Enterprise Linux 7 Extended Lifecycle Support Via RHSA-2026:14869 https://access.redhat.com/errata/RHSA-2026:14869
This issue has been addressed in the following products: Red Hat Enterprise Linux 7 Extended Lifecycle Support Via RHSA-2026:14925 https://access.redhat.com/errata/RHSA-2026:14925
This issue has been addressed in the following products: Red Hat Enterprise Linux 10.0 Extended Update Support Via RHSA-2026:15883 https://access.redhat.com/errata/RHSA-2026:15883
This issue has been addressed in the following products: Red Hat Enterprise Linux 10 Via RHSA-2026:19569 https://access.redhat.com/errata/RHSA-2026:19569
This issue has been addressed in the following products: Red Hat Enterprise Linux 9 Via RHSA-2026:19568 https://access.redhat.com/errata/RHSA-2026:19568