Linux: Use After Free
CVE-2025-38154 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 4edb40b05cb6a261775abfd8046804ca139a5546, b19cbf0b9a91f5a0d93fbcd761ff71c48ab40ed9, 4c6fa65ab2aec7df94809478c8d28ef38676a1b7 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.2% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 4edb40b05cb6a261775abfd8046804ca139a5546 or b19cbf0b9a91f5a0d93fbcd761ff71c48ab40ed9 or 4c6fa65ab2aec7df94809478c8d28ef38676a1b7 or 15c0250dae3b48a398447d2b364603821ed4ed90, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.15.186 or 6.1.142 or 6.6.94 or 6.10, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 4959ffc65a0e94f8acaac20deac49f89e6ded52d up to, but not including, 4edb40b05cb6a261775abfd8046804ca139a5546; 5eabdf17fed2ad41b836bb4055ec36d95e512c50 up to, but not including, b19cbf0b9a91f5a0d93fbcd761ff71c48ab40ed9; e946428439a0d2079959f5603256ac51b6047017 up to, but not including, 4c6fa65ab2aec7df94809478c8d28ef38676a1b7; 4b4647add7d3c8530493f7247d11e257ee425bf0 up to, but not including, 15c0250dae3b48a398447d2b364603821ed4ed90; 4b4647add7d3c8530493f7247d11e257ee425bf0 up to, but not including, 7c0a16f6ea2b1c82a03bccd5d1bdb4a7bbd4d987; 4b4647add7d3c8530493f7247d11e257ee425bf0 up to, but not including, 8259eb0e06d8f64c700f5fbdb28a5c18e10de291; 3627605de498639a3c586c8684d12c89cba11073; 5.15.162 up to, but not including, 5.15.186; and 4 more ranges | 4edb40b05cb6a261775abfd8046804ca139a5546, b19cbf0b9a91f5a0d93fbcd761ff71c48ab40ed9, 4c6fa65ab2aec7df94809478c8d28ef38676a1b7, 15c0250dae3b48a398447d2b364603821ed4ed90, 7c0a16f6ea2b1c82a03bccd5d1bdb4a7bbd4d987, 8259eb0e06d8f64c700f5fbdb28a5c18e10de291 |
| Linux | Linux Kernel | 5.15.162 up to, but not including, 5.15.186; 6.1.95 up to, but not including, 6.1.142; 6.6.35 up to, but not including, 6.6.94; 6.9.6 up to, but not including, 6.10; 6.10.1 up to, but not including, 6.12.34; 6.13 up to, but not including, 6.15.3; 6.10 | 5.15.186, 6.1.142, 6.6.94, 6.10, 6.12.34, 6.15.3 |
| Debian | Debian Linux | 11.0 | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.8 | High | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
Official 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 ... '''
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/15c0250dae3b48a398447d2b364603821ed4ed90
- git.kernel.org/stable/c/4c6fa65ab2aec7df94809478c8d28ef38676a1b7
- git.kernel.org/stable/c/4edb40b05cb6a261775abfd8046804ca139a5546
- git.kernel.org/stable/c/7c0a16f6ea2b1c82a03bccd5d1bdb4a7bbd4d987
- git.kernel.org/stable/c/8259eb0e06d8f64c700f5fbdb28a5c18e10de291
- git.kernel.org/stable/c/b19cbf0b9a91f5a0d93fbcd761ff71c48ab40ed9
Third-party and government advisories
- lists.debian.org/debian-lts-announce/2025/10/msg00008.htmlThird Party Advisory
Recent Use After Free vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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