Linux: Use After Free
CVE-2025-38211 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 013dcdf6f03bcedbaf1669e3db71c34a197715b2, bf7eff5e3a36c54bbe8aff7fd6dd7c07490b81c5, 3b4a50d733acad6831f6bd9288a76a80f70650ac 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 0.41% 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 013dcdf6f03bcedbaf1669e3db71c34a197715b2 or bf7eff5e3a36c54bbe8aff7fd6dd7c07490b81c5 or 3b4a50d733acad6831f6bd9288a76a80f70650ac or 78381dc8a6b61c9bb9987d37b4d671b99767c4a1, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.4.296 or 5.10.240 or 5.15.186 or 6.1.142, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 59c68ac31e15ad09d2cb04734e3c8c544a95f8d4 up to, but not including, 013dcdf6f03bcedbaf1669e3db71c34a197715b2; 59c68ac31e15ad09d2cb04734e3c8c544a95f8d4 up to, but not including, bf7eff5e3a36c54bbe8aff7fd6dd7c07490b81c5; 59c68ac31e15ad09d2cb04734e3c8c544a95f8d4 up to, but not including, 3b4a50d733acad6831f6bd9288a76a80f70650ac; 59c68ac31e15ad09d2cb04734e3c8c544a95f8d4 up to, but not including, 78381dc8a6b61c9bb9987d37b4d671b99767c4a1; 59c68ac31e15ad09d2cb04734e3c8c544a95f8d4 up to, but not including, 23a707bbcbea468eedb398832eeb7e8e0ceafd21; 59c68ac31e15ad09d2cb04734e3c8c544a95f8d4 up to, but not including, 764c9f69beabef8bdc651a7746c59f7a340d104f; 59c68ac31e15ad09d2cb04734e3c8c544a95f8d4 up to, but not including, fd960b5ddf4faf00da43babdd3acda68842e1f6a; 59c68ac31e15ad09d2cb04734e3c8c544a95f8d4 up to, but not including, 6883b680e703c6b2efddb4e7a8d891ce1803d06b; and 1 more ranges | 013dcdf6f03bcedbaf1669e3db71c34a197715b2, bf7eff5e3a36c54bbe8aff7fd6dd7c07490b81c5, 3b4a50d733acad6831f6bd9288a76a80f70650ac, 78381dc8a6b61c9bb9987d37b4d671b99767c4a1, 23a707bbcbea468eedb398832eeb7e8e0ceafd21, 764c9f69beabef8bdc651a7746c59f7a340d104f |
| Linux | Linux Kernel | 4.8 up to, but not including, 5.4.296; 5.5 up to, but not including, 5.10.240; 5.11 up to, but not including, 5.15.186; 5.16 up to, but not including, 6.1.142; 6.2 up to, but not including, 6.6.95; 6.7 up to, but not including, 6.12.35; 6.13 up to, but not including, 6.15.4 | 5.4.296, 5.10.240, 5.15.186, 6.1.142, 6.6.95, 6.12.35 |
| 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 | 9.8 | Critical | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: RDMA/iwcm: Fix use-after-free of work objects after cm_id destruction The commit 59c68ac31e15 ("iw_cm: free cm_id resources on the last deref") simplified cm_id resource management by freeing cm_id once all references to the cm_id were removed. The references are removed either upon completion of iw_cm event handlers or when the application destroys the cm_id. This commit introduced the use-after-free condition where cm_id_private object could still be in use by event handler works during the destruction of cm_id. The commit aee2424246f9 ("RDMA/iwcm: Fix a use-after-free related to destroying CM IDs") addressed this use-after- free by flushing all pending works at the cm_id destruction. However, still another use-after-free possibility remained. It happens with the work objects allocated for each cm_id_priv within alloc_work_entries() during cm_id creation, and subsequently freed in dealloc_work_entries() once all references to the cm_id are removed. If the cm_id's last reference is decremented in the event handler work, the work object for the work itself gets removed, and causes the use- after-free BUG below: BUG: KASAN: slab-use-after-free in __pwq_activate_work+0x1ff/0x250 Read of size 8 at addr ffff88811f9cf800 by task kworker/u16:1/147091 CPU: 2 UID: 0 PID: 147091 Comm: kworker/u16:1 Not tainted 6.15.0-rc2+ #27 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-3.fc41 04/01/2014 Workqueue: 0x0 (iw_cm_wq) Call Trace: <TASK> dump_stack_lvl+0x6a/0x90 print_report+0x174/0x554 ? __virt_addr_valid+0x208/0x430 ? __pwq_activate_work+0x1ff/0x250 kasan_report+0xae/0x170 ? __pwq_activate_work+0x1ff/0x250 __pwq_activate_work+0x1ff/0x250 pwq_dec_nr_in_flight+0x8c5/0xfb0 process_one_work+0xc11/0x1460 ? __pfx_process_one_work+0x10/0x10 ? assign_work+0x16c/0x240 worker_thread+0x5ef/0xfd0 ? __pfx_worker_thread+0x10/0x10 kthread+0x3b0/0x770 ? __pfx_kthread+0x10/0x10 ? rcu_is_watching+0x11/0xb0 ? _raw_spin_unlock_irq+0x24/0x50 ? rcu_is_watching+0x11/0xb0 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x30/0x70 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1a/0x30 </TASK> Allocated by task 147416: kasan_save_stack+0x2c/0x50 kasan_save_track+0x10/0x30 __kasan_kmalloc+0xa6/0xb0 alloc_work_entries+0xa9/0x260 [iw_cm] iw_cm_connect+0x23/0x4a0 [iw_cm] rdma_connect_locked+0xbfd/0x1920 [rdma_cm] nvme_rdma_cm_handler+0x8e5/0x1b60 [nvme_rdma] cma_cm_event_handler+0xae/0x320 [rdma_cm] cma_work_handler+0x106/0x1b0 [rdma_cm] process_one_work+0x84f/0x1460 worker_thread+0x5ef/0xfd0 kthread+0x3b0/0x770 ret_from_fork+0x30/0x70 ret_from_fork_asm+0x1a/0x30 Freed by task 147091: kasan_save_stack+0x2c/0x50 kasan_save_track+0x10/0x30 kasan_save_free_info+0x37/0x60 __kasan_slab_free+0x4b/0x70 kfree+0x13a/0x4b0 dealloc_work_entries+0x125/0x1f0 [iw_cm] iwcm_deref_id+0x6f/0xa0 [iw_cm] cm_work_handler+0x136/0x1ba0 [iw_cm] process_one_work+0x84f/0x1460 worker_thread+0x5ef/0xfd0 kthread+0x3b0/0x770 ret_from_fork+0x30/0x70 ret_from_fork_asm+0x1a/0x30 Last potentially related work creation: kasan_save_stack+0x2c/0x50 kasan_record_aux_stack+0xa3/0xb0 __queue_work+0x2ff/0x1390 queue_work_on+0x67/0xc0 cm_event_handler+0x46a/0x820 [iw_cm] siw_cm_upcall+0x330/0x650 [siw] siw_cm_work_handler+0x6b9/0x2b20 [siw] process_one_work+0x84f/0x1460 worker_thread+0x5ef/0xfd0 kthread+0x3b0/0x770 ret_from_fork+0x30/0x70 ret_from_fork_asm+0x1a/0x30 This BUG is reproducible by repeating the blktests test case nvme/061 for the rdma transport and the siw driver. To avoid the use-after-free of cm_id_private work objects, ensure that the last reference to the cm_id is decremented not in the event handler works, but in the cm_id destruction context. For that purpose, mo ---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/013dcdf6f03bcedbaf1669e3db71c34a197715b2
- git.kernel.org/stable/c/23a707bbcbea468eedb398832eeb7e8e0ceafd21
- git.kernel.org/stable/c/3b4a50d733acad6831f6bd9288a76a80f70650ac
- git.kernel.org/stable/c/6883b680e703c6b2efddb4e7a8d891ce1803d06b
- git.kernel.org/stable/c/764c9f69beabef8bdc651a7746c59f7a340d104f
- git.kernel.org/stable/c/78381dc8a6b61c9bb9987d37b4d671b99767c4a1
- git.kernel.org/stable/c/bf7eff5e3a36c54bbe8aff7fd6dd7c07490b81c5
- git.kernel.org/stable/c/fd960b5ddf4faf00da43babdd3acda68842e1f6a
Third-party and government advisories
- lists.debian.org/debian-lts-announce/2025/10/msg00007.htmlMailing List, Third Party Advisory
- lists.debian.org/debian-lts-announce/2025/10/msg00008.htmlMailing List, Third Party Advisory
Recent Use After Free vulnerabilities
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- 7.8 High severity
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