{"id":"CVE-2026-72121","title":"can: bcm: add locking when updating filter and timer values","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\ncan: bcm: add locking when updating filter and timer values\n\nKCSAN detected a simultaneous access to timer values that can be\noverwritten in bcm_rx_setup() when updatin…","severity":"high","cvss":8.8,"cvssVector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= 7595de7bc56e0e52b74e56c90f7e247bf626d628 < 96994180bd7b248b0cc698afe926e23fc1bda59b","Linux >= fbd8fdc2b218e979cfe422b139b8f74c12419d1f < caa8704a7f3cb7806331596195385437126ecb3a","Linux >= 2a437b86ac5a9893c902f30ef66815bf13587bf6 < a7c369e7da8203e2b5be12bbcac7b9ab2ed5b658","Linux >= 76c84c3728178b2d38d5604e399dfe8b0752645e < a7eb6db1cd3f7b556a301dc1265945ad112089f7","Linux >= cc55dd28c20a6611e30596019b3b2f636819a4c0 < 834cbca3b12e46887f7a9b35f1981a888360ea4c","Linux >= c2aba69d0c36a496ab4f2e81e9c2b271f2693fd7 < 19b1994069dd29478ba767de1f98f14a088198dc","Linux >= c2aba69d0c36a496ab4f2e81e9c2b271f2693fd7 < fc9f5ee1b073bd233d9c604e338af4ebb42cbc33","Linux >= c2aba69d0c36a496ab4f2e81e9c2b271f2693fd7 < 749179c2e25b95d22499ed29096b3e02d6dfd2b4","Linux 8f1c022541bf5a923c8d6fa483112c15250f30a4","Linux c4e8a172501e677ebd8ea9d9161d97dc4df56fbd","Linux >= 5.10.238 < 5.10.265","Linux >= 5.15.185 < 5.15.216","Linux >= 6.1.141 < 6.1.183","Linux >= 6.6.93 < 6.6.148","Linux >= 6.12.31 < 6.12.101","Linux >= 5.4.294 < 5.5","Linux >= 6.14.9 < 6.15","Linux 6.15"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-16T18:42:04.470904Z"},"published":"2026-08-15","updated":"2026-10-16","sourceUpdated":"2026-10-16T18:44:57.290Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-72121","references":[{"url":"https://git.kernel.org/stable/c/96994180bd7b248b0cc698afe926e23fc1bda59b"},{"url":"https://git.kernel.org/stable/c/caa8704a7f3cb7806331596195385437126ecb3a"},{"url":"https://git.kernel.org/stable/c/a7c369e7da8203e2b5be12bbcac7b9ab2ed5b658"},{"url":"https://git.kernel.org/stable/c/a7eb6db1cd3f7b556a301dc1265945ad112089f7"},{"url":"https://git.kernel.org/stable/c/834cbca3b12e46887f7a9b35f1981a888360ea4c"},{"url":"https://git.kernel.org/stable/c/19b1994069dd29478ba767de1f98f14a088198dc"},{"url":"https://git.kernel.org/stable/c/fc9f5ee1b073bd233d9c604e338af4ebb42cbc33"},{"url":"https://git.kernel.org/stable/c/749179c2e25b95d22499ed29096b3e02d6dfd2b4"}],"tags":["cve.org"],"epss":0.00354,"epssPercentile":0.27563,"ingestedAt":"2026-10-16T19:46:24.430Z","slug":"CVE-2026-72121","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\ncan: bcm: add locking when updating filter and timer values\n\nKCSAN detected a simultaneous access to timer values that can be\noverwritten in bcm_rx_setup() when updating timer and filter content\nwhile bcm_rx_handler(), bcm_rx_timeout_handler() or bcm_rx_thr_handler()\nrun concurrently on incoming CAN traffic.\n\nProtect the timer (ival1/ival2/kt_ival1/kt_ival2/kt_lastmsg) and filter\n(nframes/flags/frames/last_frames) updates in bcm_rx_setup() with a new\nper-op bcm_rx_update_lock, taken with the matching scope in the RX\nhandlers. memcpy_from_msg() is staged into a temporary buffer before the\nlock is taken, since it can sleep and must not run under a spinlock.\n\nhrtimer_cancel() is always called without bcm_rx_update_lock held, since\nbcm_rx_timeout_handler()/bcm_rx_thr_handler() take the same lock and a\nrunning callback would otherwise deadlock against the canceller.\n\nAlso close a related race: bcm_rx_setup() cleared the RTR flag in the\nstored reply frame's can_id as a separate, unprotected step after the\nframe content was already installed, so a concurrent bcm_rx_handler()\ncould transmit a stale reply with CAN_RTR_FLAG still set. Fold that\nnormalization into the initial frame preparation instead (on the staged\nbuffer for updates, directly on op->frames pre-registration for new\nops), so the installed frame is always atomically self-consistent.\n\nbcm_rx_handler()'s RX_RTR_FRAME check now takes a lock-protected\nsnapshot of op->flags before deciding whether to call bcm_can_tx(),\nbut does not hold the lock across that call.\n\nAlso take a lock-protected snapshot of the currframe in bcm_can_tx()\nto avoid partly overwrites by content updates in bcm_tx_setup().\nFinally check if a TX_RESET_MULTI_IDX/SETTIMER might have reset\nop->currframe between the two locked sections in bcm_can_tx().\n\nOmit calling hrtimer_forward() with zero interval in bcm_rx_thr_handler().\nkt_ival2 may have been concurrently cleared by bcm_rx_setup() before it\ncancels this timer, so check kt_ival2 inside the bcm_rx_update_lock.\n\n## Affected\n\n- `Linux >= 7595de7bc56e0e52b74e56c90f7e247bf626d628 < 96994180bd7b248b0cc698afe926e23fc1bda59b`\n- `Linux >= fbd8fdc2b218e979cfe422b139b8f74c12419d1f < caa8704a7f3cb7806331596195385437126ecb3a`\n- `Linux >= 2a437b86ac5a9893c902f30ef66815bf13587bf6 < a7c369e7da8203e2b5be12bbcac7b9ab2ed5b658`\n- `Linux >= 76c84c3728178b2d38d5604e399dfe8b0752645e < a7eb6db1cd3f7b556a301dc1265945ad112089f7`\n- `Linux >= cc55dd28c20a6611e30596019b3b2f636819a4c0 < 834cbca3b12e46887f7a9b35f1981a888360ea4c`\n- `Linux >= c2aba69d0c36a496ab4f2e81e9c2b271f2693fd7 < 19b1994069dd29478ba767de1f98f14a088198dc`\n- `Linux >= c2aba69d0c36a496ab4f2e81e9c2b271f2693fd7 < fc9f5ee1b073bd233d9c604e338af4ebb42cbc33`\n- `Linux >= c2aba69d0c36a496ab4f2e81e9c2b271f2693fd7 < 749179c2e25b95d22499ed29096b3e02d6dfd2b4`\n- `Linux 8f1c022541bf5a923c8d6fa483112c15250f30a4`\n- `Linux c4e8a172501e677ebd8ea9d9161d97dc4df56fbd`\n- `Linux >= 5.10.238 < 5.10.265`\n- `Linux >= 5.15.185 < 5.15.216`\n- `Linux >= 6.1.141 < 6.1.183`\n- `Linux >= 6.6.93 < 6.6.148`\n- `Linux >= 6.12.31 < 6.12.101`\n- `Linux >= 5.4.294 < 5.5`\n- `Linux >= 6.14.9 < 6.15`\n- `Linux 6.15`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":48,"depthScoreParts":{"impact":48.4,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}