Linux: Use After Free
CVE-2025-38051 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.0 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 aee067e88d61eb72e966f094e4749c6b14e7008f, a24c2f05ac3c5b0aaa539d9d913826d2643dfd0e, 1b197931fbc821bc7e9e91bf619400db563e3338 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 0.23% 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 aee067e88d61eb72e966f094e4749c6b14e7008f or a24c2f05ac3c5b0aaa539d9d913826d2643dfd0e or 1b197931fbc821bc7e9e91bf619400db563e3338 or c8623231e0edfcccb7cc6add0288fa0f0594282f, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.4.294 or 5.10.238 or 5.15.185 or 6.1.141, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | a364bc0b37f14ffd66c1f982af42990a9d77fa43 up to, but not including, aee067e88d61eb72e966f094e4749c6b14e7008f; a364bc0b37f14ffd66c1f982af42990a9d77fa43 up to, but not including, a24c2f05ac3c5b0aaa539d9d913826d2643dfd0e; a364bc0b37f14ffd66c1f982af42990a9d77fa43 up to, but not including, 1b197931fbc821bc7e9e91bf619400db563e3338; a364bc0b37f14ffd66c1f982af42990a9d77fa43 up to, but not including, c8623231e0edfcccb7cc6add0288fa0f0594282f; a364bc0b37f14ffd66c1f982af42990a9d77fa43 up to, but not including, 73cadde98f67f76c5eba00ac0b72c453383cec8b; a364bc0b37f14ffd66c1f982af42990a9d77fa43 up to, but not including, 9bea368648ac46f8593a780760362e40291d22a9; a364bc0b37f14ffd66c1f982af42990a9d77fa43 up to, but not including, 9c9aafbacc183598f064902365e107b5e856531f; a364bc0b37f14ffd66c1f982af42990a9d77fa43 up to, but not including, a7a8fe56e932a36f43e031b398aef92341bf5ea0; and 3 more ranges | aee067e88d61eb72e966f094e4749c6b14e7008f, a24c2f05ac3c5b0aaa539d9d913826d2643dfd0e, 1b197931fbc821bc7e9e91bf619400db563e3338, c8623231e0edfcccb7cc6add0288fa0f0594282f, 73cadde98f67f76c5eba00ac0b72c453383cec8b, 9bea368648ac46f8593a780760362e40291d22a9 |
| Debian | Debian Linux | 11.0 | Not stated |
| Linux | Linux Kernel | 2.6.27.4 up to, but not including, 5.4.294; 5.5 up to, but not including, 5.10.238; 5.11 up to, but not including, 5.15.185; 5.16 up to, but not including, 6.1.141; 6.2 up to, but not including, 6.6.93; 6.7 up to, but not including, 6.12.31; 6.13 up to, but not including, 6.14.9; 6.15 | 5.4.294, 5.10.238, 5.15.185, 6.1.141, 6.6.93, 6.12.31 |
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
- HighSuccess depends on conditions outside the attacker's control.
- 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:H/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 | 7.0 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: smb: client: Fix use-after-free in cifs_fill_dirent There is a race condition in the readdir concurrency process, which may access the rsp buffer after it has been released, triggering the following KASAN warning. ================================================================== BUG: KASAN: slab-use-after-free in cifs_fill_dirent+0xb03/0xb60 [cifs] Read of size 4 at addr ffff8880099b819c by task a.out/342975 CPU: 2 UID: 0 PID: 342975 Comm: a.out Not tainted 6.15.0-rc6+ #240 PREEMPT(full) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x53/0x70 print_report+0xce/0x640 kasan_report+0xb8/0xf0 cifs_fill_dirent+0xb03/0xb60 [cifs] cifs_readdir+0x12cb/0x3190 [cifs] iterate_dir+0x1a1/0x520 __x64_sys_getdents+0x134/0x220 do_syscall_64+0x4b/0x110 entry_SYSCALL_64_after_hwframe+0x76/0x7e RIP: 0033:0x7f996f64b9f9 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0d f7 c3 0c 00 f7 d8 64 89 8 RSP: 002b:00007f996f53de78 EFLAGS: 00000207 ORIG_RAX: 000000000000004e RAX: ffffffffffffffda RBX: 00007f996f53ecdc RCX: 00007f996f64b9f9 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 00007f996f53dea0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000207 R12: ffffffffffffff88 R13: 0000000000000000 R14: 00007ffc8cd9a500 R15: 00007f996f51e000 </TASK> Allocated by task 408: kasan_save_stack+0x20/0x40 kasan_save_track+0x14/0x30 __kasan_slab_alloc+0x6e/0x70 kmem_cache_alloc_noprof+0x117/0x3d0 mempool_alloc_noprof+0xf2/0x2c0 cifs_buf_get+0x36/0x80 [cifs] allocate_buffers+0x1d2/0x330 [cifs] cifs_demultiplex_thread+0x22b/0x2690 [cifs] kthread+0x394/0x720 ret_from_fork+0x34/0x70 ret_from_fork_asm+0x1a/0x30 Freed by task 342979: kasan_save_stack+0x20/0x40 kasan_save_track+0x14/0x30 kasan_save_free_info+0x3b/0x60 __kasan_slab_free+0x37/0x50 kmem_cache_free+0x2b8/0x500 cifs_buf_release+0x3c/0x70 [cifs] cifs_readdir+0x1c97/0x3190 [cifs] iterate_dir+0x1a1/0x520 __x64_sys_getdents64+0x134/0x220 do_syscall_64+0x4b/0x110 entry_SYSCALL_64_after_hwframe+0x76/0x7e The buggy address belongs to the object at ffff8880099b8000 which belongs to the cache cifs_request of size 16588 The buggy address is located 412 bytes inside of freed 16588-byte region [ffff8880099b8000, ffff8880099bc0cc) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x99b8 head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 anon flags: 0x80000000000040(head|node=0|zone=1) page_type: f5(slab) raw: 0080000000000040 ffff888001e03400 0000000000000000 dead000000000001 raw: 0000000000000000 0000000000010001 00000000f5000000 0000000000000000 head: 0080000000000040 ffff888001e03400 0000000000000000 dead000000000001 head: 0000000000000000 0000000000010001 00000000f5000000 0000000000000000 head: 0080000000000003 ffffea0000266e01 00000000ffffffff 00000000ffffffff head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8880099b8080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880099b8100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8880099b8180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8880099b8200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880099b8280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== POC is available in the link [1]. The problem triggering process is as follows: Process 1 Process 2 ----------------------------------- ---truncated---
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/1b197931fbc821bc7e9e91bf619400db563e3338
- git.kernel.org/stable/c/73cadde98f67f76c5eba00ac0b72c453383cec8b
- git.kernel.org/stable/c/9bea368648ac46f8593a780760362e40291d22a9
- git.kernel.org/stable/c/9c9aafbacc183598f064902365e107b5e856531f
- git.kernel.org/stable/c/a24c2f05ac3c5b0aaa539d9d913826d2643dfd0e
- git.kernel.org/stable/c/a7a8fe56e932a36f43e031b398aef92341bf5ea0
- git.kernel.org/stable/c/aee067e88d61eb72e966f094e4749c6b14e7008f
- git.kernel.org/stable/c/c8623231e0edfcccb7cc6add0288fa0f0594282f
Third-party and government advisories
- lists.debian.org/debian-lts-announce/2025/10/msg00007.htmlThird Party Advisory
- lists.debian.org/debian-lts-announce/2025/10/msg00008.htmlThird Party Advisory
Recent Use After Free vulnerabilities
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