CVE-2025-21909 [Medium] | Security Vulnerability in Linux Kernel

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.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-05-21	0.08%	0.02%	-0.07%
2	2026-01-26	0.02%	0.08%	+0.06%
3	2025-11-01	—	0.02%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-05-21

0.08%

0.02%

-0.07%

2026-01-26

0.02%

0.08%

+0.06%

2025-11-01

—

0.02%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
5.5	3.1	MEDIUM	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H` Click to expand Attack vector (AV:L) They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	1.8	3.6	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

5.5

3.1

MEDIUM

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

Attack vector (AV:L): They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L): A normal user session is enough; they don’t have to be admin.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

1.8

3.6

[email protected]

OS Trackers for CVE-2025-21909

vendor	priority	summary	link
`debian`	not yet assigned	CVE-2025-21909 not yet assigned priority: Debian including 2 source packages (linux, linux-6.1), 6 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 6.	https://security-tracker.debian.org/tracker/CVE-2025-21909
`redhat`	low	—	https://access.redhat.com/security/cve/CVE-2025-21909
`suse`	medium	—	https://www.suse.com/security/cve/CVE-2025-21909/
`ubuntu`	medium	CVE-2025-21909 medium priority: Ubuntu including 158 source packages (linux, linux-allwinner-5.19, …), 1551 status rows across 10 suites (bionic, focal, jammy, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 1145, released 192, ignored 154, not-affected 40, needed 20.	https://ubuntu.com/security/CVE-2025-21909

Affected software / configurations for CVE-2025-21909

Vendor	Product	Version	Raw CPE
linux	linux_kernel	>= 2.6.26, < 5.4.291	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 5.5, < 5.10.235	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 5.11, < 5.15.179	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 5.16, < 6.1.131	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.2, < 6.6.83	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.7, < 6.12.19	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.13, < 6.13.7	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	6.14	cpe:2.3:o:linux:linux_kernel:6.14:rc1::::::
linux	linux_kernel	6.14	cpe:2.3:o:linux:linux_kernel:6.14:rc2::::::
linux	linux_kernel	6.14	cpe:2.3:o:linux:linux_kernel:6.14:rc3::::::
linux	linux_kernel	6.14	cpe:2.3:o:linux:linux_kernel:6.14:rc4::::::
linux	linux_kernel	6.14	cpe:2.3:o:linux:linux_kernel:6.14:rc5::::::

References for CVE-2025-21909

URL	Tags
https://git.kernel.org/stable/c/236f41ca728f23210b31ed2d1d8a6df575a4b2d6	Patch
https://git.kernel.org/stable/c/351eb7ac53ff1cd94d893c0c4534ced2f36ae7d7	Patch
https://git.kernel.org/stable/c/49f27f29446a5bfe633dd2cc0cfebd48a1a5e77f	Patch
https://git.kernel.org/stable/c/521e55c2b0d6028861ac0a2d06aa57bb0e3ac486	Patch
https://git.kernel.org/stable/c/5ea856d93794c4afa5542defd8c61f2708dc245a	Patch
https://git.kernel.org/stable/c/ac4860141300581d3e2f6c6dafa37220f7ea9f65	Patch
https://git.kernel.org/stable/c/cd1bdcb77fdc03c253137e55bae10551b3481461	Patch
https://git.kernel.org/stable/c/ebebbb0eded2ed9a1abfa31962f6fb699e6abce7	Patch
https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html
https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html

URL

CVE-2025-21909 | wifi: nl80211: reject cooked mode if it is set along with other flags

Exploit prediction scoring system (EPSS) score for CVE-2025-21909

Common vulnerability scoring system (CVSS) metrics for CVE-2025-21909

Weakness enumeration for CVE-2025-21909

OS Trackers for CVE-2025-21909

Affected software / configurations for CVE-2025-21909

References for CVE-2025-21909