Linux: Use After Free
CVE-2026-31584 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 9a9bdaf9dc42ccca50e53f82165292f74a365c11, a8a55913552aed45108525d1851c65e1db0cc25b, f99353cd0e9f58bf17889049137b8d65fb44ebf1 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 0.13% 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 9a9bdaf9dc42ccca50e53f82165292f74a365c11 or a8a55913552aed45108525d1851c65e1db0cc25b or f99353cd0e9f58bf17889049137b8d65fb44ebf1 or 93d9a58961a9e09306857e999b3ee76aa4be67f0, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.6.136 or 6.12.83 or 6.18.24 or 6.19.14, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 0934d37596151edce115c6d0843a9ad7d5e5d232 up to, but not including, 9a9bdaf9dc42ccca50e53f82165292f74a365c11; 0934d37596151edce115c6d0843a9ad7d5e5d232 up to, but not including, a8a55913552aed45108525d1851c65e1db0cc25b; 0934d37596151edce115c6d0843a9ad7d5e5d232 up to, but not including, f99353cd0e9f58bf17889049137b8d65fb44ebf1; 0934d37596151edce115c6d0843a9ad7d5e5d232 up to, but not including, 93d9a58961a9e09306857e999b3ee76aa4be67f0; 0934d37596151edce115c6d0843a9ad7d5e5d232 up to, but not including, f1692337c6fa26e04f89b22a4d84bf5b7ada50d1; 0934d37596151edce115c6d0843a9ad7d5e5d232 up to, but not including, 76e35091ffc722ba39b303e48bc5d08abb59dd56; 6.6 | 9a9bdaf9dc42ccca50e53f82165292f74a365c11, a8a55913552aed45108525d1851c65e1db0cc25b, f99353cd0e9f58bf17889049137b8d65fb44ebf1, 93d9a58961a9e09306857e999b3ee76aa4be67f0, f1692337c6fa26e04f89b22a4d84bf5b7ada50d1, 76e35091ffc722ba39b303e48bc5d08abb59dd56 |
| Linux | Linux Kernel | before 6.6.136; 6.12 up to, but not including, 6.12.83; 6.13 up to, but not including, 6.18.24; 6.19 up to, but not including, 6.19.14; 7.0 up to, but not including, 7.0.1 | 6.6.136, 6.12.83, 6.18.24, 6.19.14, 7.0.1 |
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 CNA.
Official description
In the Linux kernel, the following vulnerability has been resolved: media: mediatek: vcodec: fix use-after-free in encoder release path The fops_vcodec_release() function frees the context structure (ctx) without first cancelling any pending or running work in ctx->encode_work. This creates a race window where the workqueue handler (mtk_venc_worker) may still be accessing the context memory after it has been freed. Race condition: CPU 0 (release path) CPU 1 (workqueue) --------------------- ------------------ fops_vcodec_release() v4l2_m2m_ctx_release() v4l2_m2m_cancel_job() // waits for m2m job "done" mtk_venc_worker() v4l2_m2m_job_finish() // m2m job "done" // BUT worker still running! // post-job_finish access: other ctx dereferences // UAF if ctx already freed // returns (job "done") kfree(ctx) // ctx freed Root cause: The v4l2_m2m_ctx_release() only waits for the m2m job lifecycle (via TRANS_RUNNING flag), not the workqueue lifecycle. After v4l2_m2m_job_finish() is called, the m2m framework considers the job complete and v4l2_m2m_ctx_release() returns, but the worker function continues executing and may still access ctx. The work is queued during encode operations via: queue_work(ctx->dev->encode_workqueue, &ctx->encode_work) The worker function accesses ctx->m2m_ctx, ctx->dev, and other ctx fields even after calling v4l2_m2m_job_finish(). This vulnerability was confirmed with KASAN by running an instrumented test module that widens the post-job_finish race window. KASAN detected: BUG: KASAN: slab-use-after-free in mtk_venc_worker+0x159/0x180 Read of size 4 at addr ffff88800326e000 by task kworker/u8:0/12 Workqueue: mtk_vcodec_enc_wq mtk_venc_worker Allocated by task 47: __kasan_kmalloc+0x7f/0x90 fops_vcodec_open+0x85/0x1a0 Freed by task 47: __kasan_slab_free+0x43/0x70 kfree+0xee/0x3a0 fops_vcodec_release+0xb7/0x190 Fix this by calling cancel_work_sync(&ctx->encode_work) before kfree(ctx). This ensures the workqueue handler is both cancelled (if pending) and synchronized (waits for any running handler to complete) before the context is freed. Placement rationale: The fix is placed after v4l2_ctrl_handler_free() and before list_del_init(&ctx->list). At this point, all m2m operations are done (v4l2_m2m_ctx_release() has returned), and we need to ensure the workqueue is synchronized before removing ctx from the list and freeing it. Note: The open error path does NOT need cancel_work_sync() because INIT_WORK() only initializes the work structure - it does not schedule it. Work is only scheduled later during device_run() operations.
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.
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/76e35091ffc722ba39b303e48bc5d08abb59dd56
- git.kernel.org/stable/c/93d9a58961a9e09306857e999b3ee76aa4be67f0
- git.kernel.org/stable/c/9a9bdaf9dc42ccca50e53f82165292f74a365c11
- git.kernel.org/stable/c/a8a55913552aed45108525d1851c65e1db0cc25b
- git.kernel.org/stable/c/f1692337c6fa26e04f89b22a4d84bf5b7ada50d1
- git.kernel.org/stable/c/f99353cd0e9f58bf17889049137b8d65fb44ebf1
Recent Use After Free vulnerabilities
- 9.8 Critical 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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