{"id":"CVE-2025-21910","title":"wifi: cfg80211: regulatory: improve invalid hints checking","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nwifi: cfg80211: regulatory: improve invalid hints checking\n\nSyzbot keeps reporting an issue [1] that occurs when erroneous symbols\nsent from userspace get through into …","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 09d989d179d0c679043556dda77c51b41a2dae7e < 62b1a9bbfebba4b4c2bb6c1ede9ef7ecee7a9ff6","Linux >= 09d989d179d0c679043556dda77c51b41a2dae7e < da3f599517ef2ea851208df3229d07728d238dc5","Linux >= 09d989d179d0c679043556dda77c51b41a2dae7e < 6a5e3b23054cee3b92683d1467e3fa83921f5622","Linux >= 09d989d179d0c679043556dda77c51b41a2dae7e < f4112cb477c727a65787a4065a75ca593bb5b2f4","Linux >= 09d989d179d0c679043556dda77c51b41a2dae7e < 35ef07112b61b06eb30683a6563c9f6378c02476","Linux >= 09d989d179d0c679043556dda77c51b41a2dae7e < be7c5f00aa7f1344293e4d48d0e12be83a2f223d","Linux >= 09d989d179d0c679043556dda77c51b41a2dae7e < 17aa34c84867f6cd181a5743e1c647e7766962a6","Linux >= 09d989d179d0c679043556dda77c51b41a2dae7e < 59b348be7597c4a9903cb003c69e37df20c04a30","Linux 2.6.34"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-11-05T20:36:42.996260Z"},"published":"2025-04-01","updated":"2026-11-05","sourceUpdated":"2026-11-05T20:41:47.606Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2025-21910","references":[{"url":"https://git.kernel.org/stable/c/62b1a9bbfebba4b4c2bb6c1ede9ef7ecee7a9ff6"},{"url":"https://git.kernel.org/stable/c/da3f599517ef2ea851208df3229d07728d238dc5"},{"url":"https://git.kernel.org/stable/c/6a5e3b23054cee3b92683d1467e3fa83921f5622"},{"url":"https://git.kernel.org/stable/c/f4112cb477c727a65787a4065a75ca593bb5b2f4"},{"url":"https://git.kernel.org/stable/c/35ef07112b61b06eb30683a6563c9f6378c02476"},{"url":"https://git.kernel.org/stable/c/be7c5f00aa7f1344293e4d48d0e12be83a2f223d"},{"url":"https://git.kernel.org/stable/c/17aa34c84867f6cd181a5743e1c647e7766962a6"},{"url":"https://git.kernel.org/stable/c/59b348be7597c4a9903cb003c69e37df20c04a30"}],"tags":["cve.org"],"epss":0.00233,"epssPercentile":0.14259,"ingestedAt":"2026-11-05T22:38:31.854Z","slug":"CVE-2025-21910","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nwifi: cfg80211: regulatory: improve invalid hints checking\n\nSyzbot keeps reporting an issue [1] that occurs when erroneous symbols\nsent from userspace get through into user_alpha2[] via\nregulatory_hint_user() call. Such invalid regulatory hints should be\nrejected.\n\nWhile a sanity check from commit 47caf685a685 (\"cfg80211: regulatory:\nreject invalid hints\") looks to be enough to deter these very cases,\nthere is a way to get around it due to 2 reasons.\n\n1) The way isalpha() works, symbols other than latin lower and\nupper letters may be used to determine a country/domain.\nFor instance, greek letters will also be considered upper/lower\nletters and for such characters isalpha() will return true as well.\nHowever, ISO-3166-1 alpha2 codes should only hold latin\ncharacters.\n\n2) While processing a user regulatory request, between\nreg_process_hint_user() and regulatory_hint_user() there happens to\nbe a call to queue_regulatory_request() which modifies letters in\nrequest->alpha2[] with toupper(). This works fine for latin symbols,\nless so for weird letter characters from the second part of _ctype[].\n\nSyzbot triggers a warning in is_user_regdom_saved() by first sending\nover an unexpected non-latin letter that gets malformed by toupper()\ninto a character that ends up failing isalpha() check.\n\nPrevent this by enhancing is_an_alpha2() to ensure that incoming\nsymbols are latin letters and nothing else.\n\n[1] Syzbot report:\n------------[ cut here ]------------\nUnexpected user alpha2: A�\nWARNING: CPU: 1 PID: 964 at net/wireless/reg.c:442 is_user_regdom_saved net/wireless/reg.c:440 [inline]\nWARNING: CPU: 1 PID: 964 at net/wireless/reg.c:442 restore_alpha2 net/wireless/reg.c:3424 [inline]\nWARNING: CPU: 1 PID: 964 at net/wireless/reg.c:442 restore_regulatory_settings+0x3c0/0x1e50 net/wireless/reg.c:3516\nModules linked in:\nCPU: 1 UID: 0 PID: 964 Comm: kworker/1:2 Not tainted 6.12.0-rc5-syzkaller-00044-gc1e939a21eb1 #0\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024\nWorkqueue: events_power_efficient crda_timeout_work\nRIP: 0010:is_user_regdom_saved net/wireless/reg.c:440 [inline]\nRIP: 0010:restore_alpha2 net/wireless/reg.c:3424 [inline]\nRIP: 0010:restore_regulatory_settings+0x3c0/0x1e50 net/wireless/reg.c:3516\n...\nCall Trace:\n <TASK>\n crda_timeout_work+0x27/0x50 net/wireless/reg.c:542\n process_one_work kernel/workqueue.c:3229 [inline]\n process_scheduled_works+0xa65/0x1850 kernel/workqueue.c:3310\n worker_thread+0x870/0xd30 kernel/workqueue.c:3391\n kthread+0x2f2/0x390 kernel/kthread.c:389\n ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:147\n ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244\n </TASK>\n\n## Affected\n\n- `Linux >= 09d989d179d0c679043556dda77c51b41a2dae7e < 62b1a9bbfebba4b4c2bb6c1ede9ef7ecee7a9ff6`\n- `Linux >= 09d989d179d0c679043556dda77c51b41a2dae7e < da3f599517ef2ea851208df3229d07728d238dc5`\n- `Linux >= 09d989d179d0c679043556dda77c51b41a2dae7e < 6a5e3b23054cee3b92683d1467e3fa83921f5622`\n- `Linux >= 09d989d179d0c679043556dda77c51b41a2dae7e < f4112cb477c727a65787a4065a75ca593bb5b2f4`\n- `Linux >= 09d989d179d0c679043556dda77c51b41a2dae7e < 35ef07112b61b06eb30683a6563c9f6378c02476`\n- `Linux >= 09d989d179d0c679043556dda77c51b41a2dae7e < be7c5f00aa7f1344293e4d48d0e12be83a2f223d`\n- `Linux >= 09d989d179d0c679043556dda77c51b41a2dae7e < 17aa34c84867f6cd181a5743e1c647e7766962a6`\n- `Linux >= 09d989d179d0c679043556dda77c51b41a2dae7e < 59b348be7597c4a9903cb003c69e37df20c04a30`\n- `Linux 2.6.34`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}