{"id":"CVE-2026-97903","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nexit: hold a reference to thread_pid across proc_flush_pid\n\nCommit 0a36bad01731 (\"release_task: kill the no longer needed\nget/put_pid(thread_pid)\") removed the referenc…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nexit: hold a reference to thread_pid across proc_flush_pid\n\nCommit 0a36bad01731 (\"release_task: kill the no longer needed\nget/put_pid(thread_pid)\") removed the referenc…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","vendor":"Linux","product":"Linux","affected":["Linux >= 0a36bad01731e71568bdd365764d38b6bd576ab0 < bcb0936862f2b653114d9bd582ca26990ef54a64","Linux >= 0a36bad01731e71568bdd365764d38b6bd576ab0 < 96803a12e8ac15f0a1b4b151db59038f12304e58","Linux >= 0a36bad01731e71568bdd365764d38b6bd576ab0 < cdd812d0683dee14ead02c9eded568685e61b23f","Linux 6.16"],"published":"2026-09-25","updated":"2026-09-25","sourceUpdated":"2026-09-25T15:18:01.960","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-97903","references":[{"url":"https://git.kernel.org/stable/c/96803a12e8ac15f0a1b4b151db59038f12304e58","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/bcb0936862f2b653114d9bd582ca26990ef54a64","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/cdd812d0683dee14ead02c9eded568685e61b23f","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd","cve.org"],"ingestedAt":"2026-09-25T11:06:38.894Z","slug":"CVE-2026-97903","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nexit: hold a reference to thread_pid across proc_flush_pid\n\nCommit 0a36bad01731 (\"release_task: kill the no longer needed\nget/put_pid(thread_pid)\") removed the reference around proc_flush_pid().\nIt assumed that free_pids(post.pids) at the end of release_task() would\nkeep thread_pid alive until then.\n\nThat assumption is wrong.  __change_pid() only records a detached PID in\npost.pids when pid_has_task() is false for every PIDTYPE.  If another task\nstill uses the exiting task's PID as its process group or session ID,\n__unhash_process() removes the exiting task's PIDTYPE_PID link but leaves\nthe PID out of post.pids.  release_task() therefore holds no reference to\nit after dropping tasklist_lock.\n\nThe other task can then remove the remaining PIDTYPE links.  Its\nfree_pids() call schedules delayed_put_pid(), and the RCU callback can free\nthe PID before the first release_task() reaches proc_flush_pid().\n\nAn unprivileged reproducer races wait4(-1) against setsid() to trigger this\nordering.  Three of three fresh v7.2 KASAN boots reported:\n\n    BUG: KASAN: slab-use-after-free in\n    proc_invalidate_siblings_dcache+0x3e2/0x3f0\n    Read of size 8 by task h7_pid_reaper/1921\n\n    Call Trace:\n     proc_invalidate_siblings_dcache\n     release_task\n     wait_consider_task\n     __do_wait\n     do_wait\n     kernel_wait4\n\n    Freed by task 0:\n     kmem_cache_free\n     put_pid\n     delayed_put_pid\n     rcu_core\n\n    Last potentially related work creation:\n     __call_rcu_common\n     free_pids\n     ksys_setsid\n\nKASAN identified a 144-byte object from the pid cache and located the bad\nread 80 bytes into the freed object, matching pid->inodes.  With an\nexplicit reference, three of three fresh boots completed without a KASAN\nreport.  The concurrent RCU callback dropped its reference while\nproc_flush_pid() was protected, and the balancing put_pid() performed the\nfinal free afterward.\n\nTake a reference before __unhash_process() clears p->thread_pid and release\nit after proc_flush_pid() completes.\n\nA tested source reproducer is available privately on request.  No\ncontrolled read or write, information leak, or privilege escalation is\nclaimed.  The mainline patch applies directly to v6.19.y and newer;\nv6.16.y through v6.18.y need a context-adjusted backport.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":210960,"id":"CVE-2026-97903","ts":1790349119136,"field":"cvss","old":null,"new":"7.8"},{"seq":210959,"id":"CVE-2026-97903","ts":1790349119136,"field":"severity","old":"none","new":"high"}]}