{"id":"CVE-2026-52946","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nfs/fcntl: fix SOFTIRQ-unsafe lock order in fasync signaling\n\nA SOFTIRQ-safe to SOFTIRQ-unsafe lock order deadlock can occur in\nsend_sigio() and send_sigurg() when a pro…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nfs/fcntl: fix SOFTIRQ-unsafe lock order in fasync signaling\n\nA SOFTIRQ-safe to SOFTIRQ-unsafe lock order deadlock can occur in\nsend_sigio() and send_sigurg() when a pro…","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-667"],"vendor":"linux","product":"linux_kernel","affected":["linux_kernel >= 2.6.12.1, < 5.10.259","linux_kernel >= 5.11, < 5.15.210","linux_kernel >= 5.16, < 6.1.176","linux_kernel >= 6.2, < 6.6.143","linux_kernel >= 6.7, < 6.12.94","linux_kernel >= 6.13, < 6.18.36","linux_kernel >= 6.19, < 7.0.13","linux_kernel >= 7.1, < 7.1.1","linux_kernel = 2.6.12"],"patched":["linux_kernel 7.1.1"],"published":"2026-06-24","updated":"2026-09-08","sourceUpdated":"2026-09-08T09:18:12.257","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-52946","references":[{"url":"https://git.kernel.org/stable/c/00633c4683828acd5256fa8d5163f440d74bbe71","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/1bee417678f1135e35b25a37734db46aa94258d2","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/20a93e397abe850c49b6fa0e8cc827b5f634a8f5","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/32dbd5ce4be3a3ed7e00f8af18795cc84fc50a33","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/36c1b57b2ecf3c61ac93f5f07bd29b6f21e226ed","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/54626335ea4174ab2d9a183b511d825f6765e47b","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/897d6a7247739fb1528f98c575df4f2e5de7f994","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/b5fa9e32fb6718f70c986ee14dd5d01b4846f331","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/bfcc8e8d8a495bb34cae9e620adfb75fb13a3954","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-019113.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"}],"tags":["nvd","cve.org"],"epss":0.00639,"epssPercentile":0.48352,"ingestedAt":"2026-06-29T13:42:11.984Z","slug":"CVE-2026-52946","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nfs/fcntl: fix SOFTIRQ-unsafe lock order in fasync signaling\n\nA SOFTIRQ-safe to SOFTIRQ-unsafe lock order deadlock can occur in\nsend_sigio() and send_sigurg() when a process group receives a signal.\n\nWhen FASYNC is configured for a process group (PIDTYPE_PGID), both\nfunctions use read_lock(&tasklist_lock) to traverse the task list.\nHowever, they are frequently called from softirq context:\n- send_sigio() via input_inject_event -> kill_fasync\n- send_sigurg() via tcp_check_urg -> sk_send_sigurg (NET_RX_SOFTIRQ)\n\nThe deadlock is caused by the rwlock writer fairness mechanism:\n1. CPU 0 (process context) holds read_lock(&tasklist_lock) in do_wait().\n2. CPU 1 (process context) attempts write_lock(&tasklist_lock) in\n   fork() or exit() and spins, which blocks all new readers.\n3. CPU 0 is interrupted by a softirq (e.g., TCP URG packet reception).\n4. The softirq calls send_sigurg() and attempts to acquire\n   read_lock(&tasklist_lock), deadlocking because CPU 1 is waiting.\n\nSince PID hashing and do_each_pid_task() traversals are already\nRCU-protected, the read_lock on tasklist_lock is no longer strictly\nrequired for safe traversal. Fix this by replacing tasklist_lock with\nrcu_read_lock(), aligning the process group signaling path with the\nsingle-PID path. This also mitigates a potential remote denial of\nservice vector via TCP URG packets.\n\nLockdep splat:\n=====================================================\nWARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected\n[...]\nChain exists of:\n  &dev->event_lock --> &f_owner->lock --> tasklist_lock\n\nPossible interrupt unsafe locking scenario:\n       CPU0                    CPU1\n       ----                    ----\n  lock(tasklist_lock);\n                           local_irq_disable();\n                           lock(&dev->event_lock);\n                           lock(&f_owner->lock);\n  <Interrupt>\n    lock(&dev->event_lock);\n\n*** DEADLOCK ***\n\n## Affected\n\n- `linux_kernel >= 2.6.12.1, < 5.10.259`\n- `linux_kernel >= 5.11, < 5.15.210`\n- `linux_kernel >= 5.16, < 6.1.176`\n- `linux_kernel >= 6.2, < 6.6.143`\n- `linux_kernel >= 6.7, < 6.12.94`\n- `linux_kernel >= 6.13, < 6.18.36`\n- `linux_kernel >= 6.19, < 7.0.13`\n- `linux_kernel >= 7.1, < 7.1.1`\n- `linux_kernel = 2.6.12`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `linux_kernel 7.1.1`","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}