CVE-2026-89674
CriticalCVSS 9.8Exploitation Probability (EPSS)
Low risk6th percentile - higher than 6% of all known CVEs
Summary
In the Linux kernel, nfsd4_ff_encode_layoutget() has multiple XDR buffer size calculation errors. These errors can result in an out-of-bounds write or leaking uninitialized kernel memory to the client. The worst case occurs with short strings, where the function writes up to 5 bytes past the reserved XDR buffer.
Risk Assessment
This can lead to leaking sensitive kernel memory to the NFS client or kernel memory corruption. The vulnerability is remotely triggerable via NFS layoutget operations.
Recommendation
Update the Linux kernel to a version containing the fix that explicitly breaks out every encoded field and uses xdr_align_size() for variable-length opaque fields. Restrict access to NFS services to trusted networks.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: nfsd: fix XDR length calculation in nfsd4_ff_encode_layoutget The XDR buffer size calculation in nfsd4_ff_encode_layoutget() has multiple errors that can result in either an out-of-bounds write or leaking uninitialized kernel memory to the client: - fh_len doesn't account for XDR padding on the file handle data - uid and gid lengths use "8 + len" but xdr_encode_opaque() actually writes "4 + xdr_align_size(len)" bytes - ds_len omits the flags and stats_collect_hint fields (8 bytes), while len's header constant overestimates by 8 bytes -- these partially cancel but leave a net mismatch The worst case occurs with short strings (e.g. uid=0, gid=0 with an odd-sized file handle), where the function writes up to 5 bytes past the reserved XDR buffer. Conversely, when string lengths happen to be 4-byte aligned, the reservation is too large and stale buffer content is sent to the client. Fix this by breaking out every encoded field explicitly in the ds_len calculation, using xdr_align_size() for all variable-length opaque fields, and correcting the header constants.