CVE-2025-21726: linux kernel Use-After-Free — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: padata: avoid UAF for reorder_work Although the previous patch can avoid ps and ps UAF for _do_serial, it can not avoid potential UAF issue for reorder_work. This issue can happen just as below: crypto_request crypto_request crypto_del_alg padata_do_serial ... padata_reorder // processes all remaining // requests then breaks while (1) { if (!padata) break; ... } padata_do_serial // new request added list_add // sees the new request queue_work(reorder_work) padata_reorder queue_work_on(squeue->work) ... <kworker context> padata_serial_worker // completes new request, // no more outstanding // requests crypto_del_alg // free pd <kworker context> invoke_padata_reorder // UAF of pd To avoid UAF for 'reorder_work', get 'pd' ref before put 'reorder_work' into the 'serial_wq' and put 'pd' ref until the 'serial_wq' finish.

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CVSS v3.1 Score

7.8

HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Weakness Type (CWE)

CWE-416 Use After Free

Affected Products

Vendor	Product	Versions
linux	linux_kernel	5.4.19 — 5.5
linux	linux_kernel	5.5.3 — 5.10.235
linux	linux_kernel	5.11 — 5.15.79
linux	linux_kernel	5.16 — 6.1.129
linux	linux_kernel	6.2 — 6.6.76
linux	linux_kernel	6.7 — 6.12.13
linux	linux_kernel	6.13 — 6.13.2

References

Advisories & Patches

https://git.kernel.org/stable/c/4c6209efea2208597dbd3e52dc87a0d1a8f2dbe1 https://git.kernel.org/stable/c/6f45ef616775b0ce7889b0f6077fc8d681ab30bc https://git.kernel.org/stable/c/7000507bb0d2ceb545c0a690e0c707c897d102c2 https://git.kernel.org/stable/c/8ca38d0ca8c3d30dd18d311f1a7ec5cb56972cac https://git.kernel.org/stable/c/a54091c24220a4cd847d5b4f36d678edacddbaf0 https://git.kernel.org/stable/c/dd7d37ccf6b11f3d95e797ebe4e9e886d0332600 https://git.kernel.org/stable/c/f4f1b1169fc3694f9bc3e28c6c68dbbf4cc744c0

Other References

https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html https://cert-portal.siemens.com/productcert/html/ssa-265688.html

Frequently Asked Questions

What is CVE-2025-21726? +

In the Linux kernel, the following vulnerability has been resolved: padata: avoid UAF for reorder_work Although the previous patch can avoid ps and ps UAF for _do_serial, it can not avoid potential UAF issue for reorder_work. This issue can happen just as below: crypto_request crypto_request crypto_del_alg padata_do_serial ... padata_reorder // processes all remaining // requests then breaks while (1) { if (!padata) break; ... } padata_do_serial // new request added list_add // sees the new request queue_work(reorder_work) padata_reorder queue_work_on(squeue->work) ... <kworker context> padata_serial_worker // completes new request, // no more outstanding // requests crypto_del_alg // free pd <kworker context> invoke_padata_reorder // UAF of pd To avoid UAF for 'reorder_work', get 'pd' ref before put 'reorder_work' into the 'serial_wq' and put 'pd' ref until the 'serial_wq' finish. It has a CVSS v3.1 base score of 7.8 (HIGH).

How severe is CVE-2025-21726? +

CVE-2025-21726 has a CVSS v3.1 score of 7.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2025-21726? +

CVE-2025-21726 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-21726? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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