{"id":"CVE-2026-72069","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-72069","summary":"locking/rt: Fix the incorrect RCU protection in rt_spin_unlock()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nlocking/rt: Fix the incorrect RCU protection in rt_spin_unlock()\n\nrt_spin_unlock() releases the RCU protection before unlocking the\nlock. That opens the door for the following UAF scenario:\n\n T1\t\t\t\t\tT2\n spin_lock(&p->lock);\t\trcu_read_lock();\n invalidate(p);\t\t\tp = rcu_dereference(ptr);\n rcu_assign_pointer(ptr, NULL);\tif (!p) return;\n spin_unlock(&p->lock);\t\tspin_lock(&p->lock)\n \t\t\t\t   lock(&lock->lock);\n\t\t\t\t   rcu_read_lock();\n kfree_rcu(p);\t\t\trcu_read_unlock();\n\t\t\t\t....\n\t\t\t\tspin_unlock(&p->lock)\n\t\t\t\t  rcu_read_unlock(); // Ends grace period\n rcu_do_batch()\n   kfree(p);\n\t\t\t    UAF ->\t  rt_mutex_cmpxchg_release(&lock->lock...)\n\nRegular spinlocks keep preemption disabled accross the unlock operation,\nwhich provides full RCU protection, but the RT substitution fails to\nresemble that. Same applies for the rwlock substitution.\n\nMove the rcu_read_unlock() invocation past the unlock operations to match\nthe non-RT semantics. This makes it asymmetric vs. rt_xxx_lock(), but\nthat's harmless as the caller needs to hold RCU read lock across the lock\noperation. The migrate_enable() call stays before the unlock operation\nbecause there is no per CPU operation in the unlock path which would\nrequire migration to be kept disabled.","published":"2026-08-15T05:52:21.752Z","modified":"2026-08-18T03:56:19.440647152Z","cvss":{"score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Linux","name":"Kernel","fixedVersion":"6.6.148"}],"fix":null,"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/1f0d56d3f1e88f20f6e46109402f8c15d59bac37"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3cfaac77b3c32ac3940df28866de263c3f45d24c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/633cadbc0b8323f5cc140a285d2432089dbb534e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/83f9fb561c1c3917e19f95523dd933c7d30291aa"},{"type":"WEB","url":"https://git.kernel.org/stable/c/89038cc87d80c77e7aa6f42a64b2573b74af339f"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72069.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-72069"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-18T03:56:19.440647152Z"}}