CVE-2026-89543
Low risk· EPSS 10%Exploitation Probability (EPSS)
Low risk10th percentile - higher than 10% of all known CVEs
Summary
A use-after-free vulnerability exists in the Linux kernel in __rpc_clnt_handle_event and __rpc_clnt_remove_pipedir within the sunrpc subsystem. The clnt->pipefs_sb field is not refreshed on mount events nor cleared on unmount, causing comparison against a stale pointer and skipped cleanup. As a result, pipefs dentries may point to a freed rpc_clnt, leading to use-after-free during subsequent rpc_info_open() or rpc_show_info() calls.
Risk Assessment
Can lead to kernel memory corruption, system crash (panic), or potential privilege escalation by a local attacker. Affects systems using NFS/SUNRPC with pipefs.
Recommendation
Update the Linux kernel to a version containing the fix that properly updates clnt->pipefs_sb on mount events and clears it during unmount or failure paths.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: sunrpc: fix use-after-free in __rpc_clnt_handle_event and __rpc_clnt_remove_pipedir Normal client creation goes through rpc_setup_pipedir(), which records clnt->pipefs_sb, but the mount-event path in __rpc_clnt_handle_event() calls rpc_setup_pipedir_sb() directly and never refreshes that field. The umount path also removes the directory without clearing clnt->pipefs_sb. After a late pipefs mount or any remount, rpc_clnt_remove_pipedir() compares the current superblock against a stale pipefs_sb pointer and skips cleanup, leaving pipefs dentries whose inode private data still points at a freed rpc_clnt, leading to a potential use-after-free during subsequent rpc_info_open() or rpc_show_info() calls. Fix this by properly updating clnt->pipefs_sb upon mount events and clearing it during unmount or failure paths.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS