{"id":"CVE-2026-97938","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nreboot: fix cad_pid use-after-free race\n\ncad_pid is a single kernel-wide struct pid pointer","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nreboot: fix cad_pid use-after-free race\n\ncad_pid is a single kernel-wide struct pid pointer. proc_do_cad_pid()\nreads it and passes it to pid_vnr() without protecting th…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 9ec52099e4b8678a60e9f93e41ad87885d64f3e6 < ad72e2566643fff7f01666d845fb026898155e1f","Linux >= 9ec52099e4b8678a60e9f93e41ad87885d64f3e6 < 9a17b0e053197a6a42cdc75e75a35b17aa662088","Linux >= 9ec52099e4b8678a60e9f93e41ad87885d64f3e6 < 5a88f78df753993469dab4d1831f8fb4256a9468","Linux 2.6.19"],"published":"2026-09-25","updated":"2026-09-25","sourceUpdated":"2026-09-25T11:17:21.193","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-97938","references":[{"url":"https://git.kernel.org/stable/c/5a88f78df753993469dab4d1831f8fb4256a9468","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/9a17b0e053197a6a42cdc75e75a35b17aa662088","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/ad72e2566643fff7f01666d845fb026898155e1f","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd","cve.org"],"ingestedAt":"2026-09-25T11:06:38.883Z","slug":"CVE-2026-97938","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nreboot: fix cad_pid use-after-free race\n\ncad_pid is a single kernel-wide struct pid pointer. proc_do_cad_pid()\nreads it and passes it to pid_vnr() without protecting the lifetime of\nthe referenced struct pid. A concurrent writer can replace cad_pid and\ndrop the final reference to the old struct pid after the reader has\nloaded the pointer but before pid_vnr() has finished dereferencing it,\ncausing a use-after-free.\n\nkill_cad_pid() has the same lifetime race when it passes cad_pid to\nkill_pid().\n\nAt the time this issue was reported, an unprivileged user could reach the\nsysctl through user and PID namespaces because cad_pid was registered in\npid_table[]. Moving cad_pid back to the global reboot sysctl table\ncorrected that namespace and permission mismatch, but did not fix the\nunderlying lifetime race.\n\nFix this by treating cad_pid as an RCU-protected pointer at both read\nsites and by waiting for a grace period before dropping the old reference\non the write side.\n\ncall_rcu(&old_pid->rcu, ...) cannot be used here because free_pid()\nalso queues pid->rcu; queueing the same rcu_head twice can corrupt the\nRCU callback list.\n\nOriginal KASAN crash stack:\n  kernel/pid.c:545 pid_nr_ns()        # reads freed pid->level\n  kernel/pid.c:556 pid_vnr()          # calls pid_nr_ns()\n  kernel/pid.c:775 proc_do_cad_pid()  # calls pid_vnr(cad_pid)\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":[]}