Executive brief
The Linux kernel's NFS server daemon (nfsd) contains a memory buffer overrun in its tracepoint logging code. When serving NFS requests over UDP, the kernel can write logging data beyond the allocated buffer size, potentially corrupting kernel memory. This could allow an attacker to crash the NFS server or execute arbitrary code with kernel privileges through malicious NFS requests.
Technical details
The vulnerability exists in the nfsd_fh_verify and nfsd_fh_verify_err tracepoints, which declare a server sockaddr slot sized by xpt_remotelen but fill it with data from xpt_local using xpt_locallen. When xpt_locallen exceeds xpt_remotelen (which occurs on NFS/UDP where xpt_remotelen remains 0), the __assign_sockaddr memcpy writes past the reserved ring-buffer slot, causing a heap buffer overflow. The vulnerability is reachable on all NFSv2/v3-over-UDP requests, where 16 or 28 bytes are copied into a zero-byte slot. The fix sizes the server slot declaration with xpt_locallen to match the actual copy length, consistent with other NFSD tracepoints.
Affected products
- Linux Linux kernel affected versions unspecified in advisory
Timeline
- 2026-09-11: disclosed
- 2026-09-11: advisory: CVE-2026-89702 published