Skip to content
Fencer Vulns
medium 5.5

CVE-2025-21910 json

wifi: cfg80211: regulatory: improve invalid hints checking

published 2025-04-01 19 mo ago modified 2026-11-05 3 d ago also EUVD-2025-9411

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 14%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

wifi: cfg80211: regulatory: improve invalid hints checking

Syzbot keeps reporting an issue [1] that occurs when erroneous symbols sent from userspace get through into user_alpha2[] via regulatory_hint_user() call. Such invalid regulatory hints should be rejected.

While a sanity check from commit 47caf685a685 ("cfg80211: regulatory: reject invalid hints") looks to be enough to deter these very cases, there is a way to get around it due to 2 reasons.

1) The way isalpha() works, symbols other than latin lower and upper letters may be used to determine a country/domain. For instance, greek letters will also be considered upper/lower letters and for such characters isalpha() will return true as well. However, ISO-3166-1 alpha2 codes should only hold latin characters.

2) While processing a user regulatory request, between reg_process_hint_user() and regulatory_hint_user() there happens to be a call to queue_regulatory_request() which modifies letters in request->alpha2[] with toupper(). This works fine for latin symbols, less so for weird letter characters from the second part of _ctype[].

Syzbot triggers a warning in is_user_regdom_saved() by first sending over an unexpected non-latin letter that gets malformed by toupper() into a character that ends up failing isalpha() check.

Prevent this by enhancing is_an_alpha2() to ensure that incoming symbols are latin letters and nothing else.

[1] Syzbot report: ------------[ cut here ]------------ Unexpected user alpha2: A� WARNING: CPU: 1 PID: 964 at net/wireless/reg.c:442 is_user_regdom_saved net/wireless/reg.c:440 [inline] WARNING: CPU: 1 PID: 964 at net/wireless/reg.c:442 restore_alpha2 net/wireless/reg.c:3424 [inline] WARNING: CPU: 1 PID: 964 at net/wireless/reg.c:442 restore_regulatory_settings+0x3c0/0x1e50 net/wireless/reg.c:3516 Modules linked in: CPU: 1 UID: 0 PID: 964 Comm: kworker/1:2 Not tainted 6.12.0-rc5-syzkaller-00044-gc1e939a21eb1 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 Workqueue: events_power_efficient crda_timeout_work RIP: 0010:is_user_regdom_saved net/wireless/reg.c:440 [inline] RIP: 0010:restore_alpha2 net/wireless/reg.c:3424 [inline] RIP: 0010:restore_regulatory_settings+0x3c0/0x1e50 net/wireless/reg.c:3516 ... Call Trace: <TASK> crda_timeout_work+0x27/0x50 net/wireless/reg.c:542 process_one_work kernel/workqueue.c:3229 [inline] process_scheduled_works+0xa65/0x1850 kernel/workqueue.c:3310 worker_thread+0x870/0xd30 kernel/workqueue.c:3391 kthread+0x2f2/0x390 kernel/kthread.c:389 ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 </TASK>

Patch / fix

  • Linux Linux 5.4.291, 5.10.235, 5.15.179, 6.1.131, 6.6.83, 6.12.19, 6.13.7, 6.14
  • linux Debian 12 6.1.133-1
  • linux Debian 14, Debian 13 6.12.19-1

debian advisories DEBIAN-CVE-2025-21910

  • linux Ubuntu 20.04 LTS 5.4.0-216.236
  • linux Ubuntu 22.04 LTS 5.15.0-140.150
  • linux Ubuntu 24.04 LTS 6.8.0-84.84
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1146.156
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1084.91
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1039.41
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1149.158
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1083.92

ubuntu advisories UBUNTU-CVE-2025-21910

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.20.3.1
  • kernel-syms-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.20.3.1
  • kernel-source-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.20.3.1
  • kernel-rt Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.39.1
  • kernel-syms-rt Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.39.1
  • kernel-rt_debug Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.39.1
  • kernel-source-rt Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.39.1
  • kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.3.1

suse advisories SUSE-SU-2025:01967-1SUSE-SU-2025:01964-1SUSE-SU-2025:01951-1SUSE-SU-2025:01919-1SUSE-SU-2025:01707-1SUSE-SU-2025:01614-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-21910 updated cvss 4.3

kernel: wifi: cfg80211: regulatory: improve invalid hints checking

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
    affected: no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
3 d ago

Exploit prediction

0.23% chance of exploitation in the next 30 days, higher than 14% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.