{"id":"CVE-2026-97938","state":"PUBLISHED","title":"reboot: fix cad_pid use-after-free race","description":"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 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)","publishedAt":"2026-09-25T10:22:51.720Z","updatedAt":"2026-10-21T12:53:45.385Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"9ec52099e4b8678a60e9f93e41ad87885d64f3e6","status":"affected","lessThan":"0c1a966bc047af2801a70b8eb13f9df5d7ab925f","versionType":"git"},{"version":"9ec52099e4b8678a60e9f93e41ad87885d64f3e6","status":"affected","lessThan":"ae3e53fe3c1241855e3a88f74877738349948c78","versionType":"git"},{"version":"9ec52099e4b8678a60e9f93e41ad87885d64f3e6","status":"affected","lessThan":"ad72e2566643fff7f01666d845fb026898155e1f","versionType":"git"},{"version":"9ec52099e4b8678a60e9f93e41ad87885d64f3e6","status":"affected","lessThan":"9a17b0e053197a6a42cdc75e75a35b17aa662088","versionType":"git"},{"version":"9ec52099e4b8678a60e9f93e41ad87885d64f3e6","status":"affected","lessThan":"5a88f78df753993469dab4d1831f8fb4256a9468","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/linux/sched.h","include/linux/sched/signal.h","init/main.c","kernel/reboot.c","kernel/signal.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.19","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.19","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.112","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.53","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.7","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/linux/sched.h","include/linux/sched/signal.h","init/main.c","kernel/reboot.c","kernel/signal.c"]}],"references":["https://git.kernel.org/stable/c/0c1a966bc047af2801a70b8eb13f9df5d7ab925f","https://git.kernel.org/stable/c/ae3e53fe3c1241855e3a88f74877738349948c78","https://git.kernel.org/stable/c/ad72e2566643fff7f01666d845fb026898155e1f","https://git.kernel.org/stable/c/9a17b0e053197a6a42cdc75e75a35b17aa662088","https://git.kernel.org/stable/c/5a88f78df753993469dab4d1831f8fb4256a9468"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:43.249Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/97xxx/CVE-2026-97938.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-97938","state":"PUBLISHED","datePublished":"2026-09-25T10:22:51.720Z","dateUpdated":"2026-10-21T12:53:45.385Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:18:58.204Z"},"containers":{"cna":{"title":"reboot: fix cad_pid use-after-free race","descriptions":[{"lang":"en","value":"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 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)"}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"9ec52099e4b8678a60e9f93e41ad87885d64f3e6","status":"affected","lessThan":"0c1a966bc047af2801a70b8eb13f9df5d7ab925f","versionType":"git"},{"version":"9ec52099e4b8678a60e9f93e41ad87885d64f3e6","status":"affected","lessThan":"ae3e53fe3c1241855e3a88f74877738349948c78","versionType":"git"},{"version":"9ec52099e4b8678a60e9f93e41ad87885d64f3e6","status":"affected","lessThan":"ad72e2566643fff7f01666d845fb026898155e1f","versionType":"git"},{"version":"9ec52099e4b8678a60e9f93e41ad87885d64f3e6","status":"affected","lessThan":"9a17b0e053197a6a42cdc75e75a35b17aa662088","versionType":"git"},{"version":"9ec52099e4b8678a60e9f93e41ad87885d64f3e6","status":"affected","lessThan":"5a88f78df753993469dab4d1831f8fb4256a9468","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/linux/sched.h","include/linux/sched/signal.h","init/main.c","kernel/reboot.c","kernel/signal.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.19","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.19","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.112","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.53","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.7","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/linux/sched.h","include/linux/sched/signal.h","init/main.c","kernel/reboot.c","kernel/signal.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/0c1a966bc047af2801a70b8eb13f9df5d7ab925f"},{"url":"https://git.kernel.org/stable/c/ae3e53fe3c1241855e3a88f74877738349948c78"},{"url":"https://git.kernel.org/stable/c/ad72e2566643fff7f01666d845fb026898155e1f"},{"url":"https://git.kernel.org/stable/c/9a17b0e053197a6a42cdc75e75a35b17aa662088"},{"url":"https://git.kernel.org/stable/c/5a88f78df753993469dab4d1831f8fb4256a9468"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-21T12:53:45.385Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.19","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.19","versionEndExcluding":"6.12.112"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.19","versionEndExcluding":"6.18.53"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.19","versionEndExcluding":"7.2.7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.19","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}