CVE-2025-21909: linux kernel — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: wifi: nl80211: reject cooked mode if it is set along with other flags It is possible to set both MONITOR_FLAG_COOK_FRAMES and MONITOR_FLAG_ACTIVE flags simultaneously on the same monitor interface from the userspace. This causes a sub-interface to be created with no IEEE80211_SDATA_IN_DRIVER bit set because the monitor interface is in the cooked state and it takes precedence over all other states. When the interface is then being deleted the kernel calls WARN_ONCE() from check_sdata_in_driver() because of missing that bit. Fix this by rejecting MONITOR_FLAG_COOK_FRAMES if it is set along with other flags. Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

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CVSS v3.1 Score

5.5

MEDIUM

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

Weakness Type (CWE)

CWE-362 CWE-362

Affected Products

Vendor	Product	Versions
linux	linux_kernel	2.6.26 — 5.4.291
linux	linux_kernel	5.5 — 5.10.235
linux	linux_kernel	5.11 — 5.15.179
linux	linux_kernel	5.16 — 6.1.131
linux	linux_kernel	6.2 — 6.6.83
linux	linux_kernel	6.7 — 6.12.19
linux	linux_kernel	6.13 — 6.13.7
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/236f41ca728f23210b31ed2d1d8a6df575a4b2d6 https://git.kernel.org/stable/c/351eb7ac53ff1cd94d893c0c4534ced2f36ae7d7 https://git.kernel.org/stable/c/49f27f29446a5bfe633dd2cc0cfebd48a1a5e77f https://git.kernel.org/stable/c/521e55c2b0d6028861ac0a2d06aa57bb0e3ac486 https://git.kernel.org/stable/c/5ea856d93794c4afa5542defd8c61f2708dc245a https://git.kernel.org/stable/c/ac4860141300581d3e2f6c6dafa37220f7ea9f65 https://git.kernel.org/stable/c/cd1bdcb77fdc03c253137e55bae10551b3481461 https://git.kernel.org/stable/c/ebebbb0eded2ed9a1abfa31962f6fb699e6abce7

Other References

https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html

Frequently Asked Questions

What is CVE-2025-21909? +

In the Linux kernel, the following vulnerability has been resolved: wifi: nl80211: reject cooked mode if it is set along with other flags It is possible to set both MONITOR_FLAG_COOK_FRAMES and MONITOR_FLAG_ACTIVE flags simultaneously on the same monitor interface from the userspace. This causes a sub-interface to be created with no IEEE80211_SDATA_IN_DRIVER bit set because the monitor interface is in the cooked state and it takes precedence over all other states. When the interface is then being deleted the kernel calls WARN_ONCE() from check_sdata_in_driver() because of missing that bit. Fix this by rejecting MONITOR_FLAG_COOK_FRAMES if it is set along with other flags. Found by Linux Verification Center (linuxtesting.org) with Syzkaller. It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2025-21909? +

CVE-2025-21909 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-21909? +

CVE-2025-21909 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-2025-21909? +

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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