{"id":"CVE-2025-40201","state":"PUBLISHED","title":"kernel/sys.c: fix the racy usage of task_lock(tsk->group_leader) in sys_prlimit64() paths","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nkernel/sys.c: fix the racy usage of task_lock(tsk->group_leader) in sys_prlimit64() paths\n\nThe usage of task_lock(tsk->group_leader) in sys_prlimit64()->do_prlimit()\npath is very broken.\n\nsys_prlimit64() does get_task_struct(tsk) but this only protects task_struct\nitself. If tsk != current and tsk is not a leader, this process can exit/exec\nand task_lock(tsk->group_leader) may use the already freed task_struct.\n\nAnother problem is that sys_prlimit64() can race with mt-exec which changes\n->group_leader. In this case do_prlimit() may take the wrong lock, or (worse)\n->group_leader may change between task_lock() and task_unlock().\n\nChange sys_prlimit64() to take tasklist_lock when necessary. This is not\nnice, but I don't see a better fix for -stable.","publishedAt":"2025-11-12T21:56:34.063Z","updatedAt":"2026-10-15T22:02:40.564Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"18c91bb2d87268d23868bf13508f5bc9cf04e89a","status":"affected","lessThan":"1bc0d9315ef5296abb2c9fd840336255850ded18","versionType":"git"},{"version":"18c91bb2d87268d23868bf13508f5bc9cf04e89a","status":"affected","lessThan":"132f827e7bac7373e1522e89709d70b43cae5342","versionType":"git"},{"version":"18c91bb2d87268d23868bf13508f5bc9cf04e89a","status":"affected","lessThan":"19b45c84bd9fd42fa97ff80c6350d604cb871c75","versionType":"git"},{"version":"18c91bb2d87268d23868bf13508f5bc9cf04e89a","status":"affected","lessThan":"6796412decd2d8de8ec708213bbc958fab72f143","versionType":"git"},{"version":"18c91bb2d87268d23868bf13508f5bc9cf04e89a","status":"affected","lessThan":"a15f37a40145c986cdf289a4b88390f35efdecc4","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/sys.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.18","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.18","versionType":"semver"},{"version":"6.1.157","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.113","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.54","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.17.4","status":"unaffected","lessThanOrEqual":"6.17.*","versionType":"semver"},{"version":"6.18","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/sys.c"]}],"references":["https://git.kernel.org/stable/c/1bc0d9315ef5296abb2c9fd840336255850ded18","https://git.kernel.org/stable/c/132f827e7bac7373e1522e89709d70b43cae5342","https://git.kernel.org/stable/c/19b45c84bd9fd42fa97ff80c6350d604cb871c75","https://git.kernel.org/stable/c/6796412decd2d8de8ec708213bbc958fab72f143","https://git.kernel.org/stable/c/a15f37a40145c986cdf289a4b88390f35efdecc4"],"weaknesses":[],"ingestedAt":"2026-10-29T20:09:09.358Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2025/40xxx/CVE-2025-40201.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-40201","state":"PUBLISHED","datePublished":"2025-11-12T21:56:34.063Z","dateUpdated":"2026-10-15T22:02:40.564Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2025-04-16T07:20:57.178Z"},"containers":{"cna":{"title":"kernel/sys.c: fix the racy usage of task_lock(tsk->group_leader) in sys_prlimit64() paths","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nkernel/sys.c: fix the racy usage of task_lock(tsk->group_leader) in sys_prlimit64() paths\n\nThe usage of task_lock(tsk->group_leader) in sys_prlimit64()->do_prlimit()\npath is very broken.\n\nsys_prlimit64() does get_task_struct(tsk) but this only protects task_struct\nitself. If tsk != current and tsk is not a leader, this process can exit/exec\nand task_lock(tsk->group_leader) may use the already freed task_struct.\n\nAnother problem is that sys_prlimit64() can race with mt-exec which changes\n->group_leader. In this case do_prlimit() may take the wrong lock, or (worse)\n->group_leader may change between task_lock() and task_unlock().\n\nChange sys_prlimit64() to take tasklist_lock when necessary. This is not\nnice, but I don't see a better fix for -stable."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"18c91bb2d87268d23868bf13508f5bc9cf04e89a","status":"affected","lessThan":"1bc0d9315ef5296abb2c9fd840336255850ded18","versionType":"git"},{"version":"18c91bb2d87268d23868bf13508f5bc9cf04e89a","status":"affected","lessThan":"132f827e7bac7373e1522e89709d70b43cae5342","versionType":"git"},{"version":"18c91bb2d87268d23868bf13508f5bc9cf04e89a","status":"affected","lessThan":"19b45c84bd9fd42fa97ff80c6350d604cb871c75","versionType":"git"},{"version":"18c91bb2d87268d23868bf13508f5bc9cf04e89a","status":"affected","lessThan":"6796412decd2d8de8ec708213bbc958fab72f143","versionType":"git"},{"version":"18c91bb2d87268d23868bf13508f5bc9cf04e89a","status":"affected","lessThan":"a15f37a40145c986cdf289a4b88390f35efdecc4","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/sys.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.18","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.18","versionType":"semver"},{"version":"6.1.157","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.113","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.54","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.17.4","status":"unaffected","lessThanOrEqual":"6.17.*","versionType":"semver"},{"version":"6.18","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/sys.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/1bc0d9315ef5296abb2c9fd840336255850ded18"},{"url":"https://git.kernel.org/stable/c/132f827e7bac7373e1522e89709d70b43cae5342"},{"url":"https://git.kernel.org/stable/c/19b45c84bd9fd42fa97ff80c6350d604cb871c75"},{"url":"https://git.kernel.org/stable/c/6796412decd2d8de8ec708213bbc958fab72f143"},{"url":"https://git.kernel.org/stable/c/a15f37a40145c986cdf289a4b88390f35efdecc4"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The vulnerability is reached through the `prlimit64()` syscall (and pid-targeted setrlimit paths) from a local process; no network or physical vector is involved.\nAC:L - The attacker drives both sides of the race using their own processes — one loop calling prlimit64() on a non-leader TID while a co-operating multithreaded process repeatedly performs mt-exec or group-exit-and-reap — and can retry indefinitely until the window is hit.\nPR:L - check_prlimit_permission() grants access on a plain uid/gid match, so any unprivileged local user can target a non-leader thread of a process they own; no CAP_SYS_RESOURCE or root is required, and it works unrestricted inside containers.\nUI:N - The attacker creates the victim threads, the exec/exit, and the racing syscall entirely on their own; no action by any other user is needed.\nS:U - The corruption and its consequences stay within the kernel's own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - Use-after-free on a task_struct: update_rlimit_cpu() dereferences the freed leader's ->sighand/->signal, and an attacker who reallocates the slot via fork() spraying can leverage the dangling-pointer reads for kernel memory disclosure.\nI:H - The UAF gives write primitives — spin_lock/spin_unlock words written into freed memory plus an attacker-supplied RLIMIT_CPU value written through a dangling sighand/signal pointer — sufficient to corrupt a reallocated live task_struct and pursue control-flow hijack.\nA:H - The mismatched task_lock()/task_unlock() across a de_thread() leaves a task's alloc_lock permanently held, deadlocking every subsequent task_lock() user (/proc readers, exec, fs_struct access), and the UAF itself readily oopses/panics the kernel."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:08:29.919Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.18","versionEndExcluding":"6.1.157"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.18","versionEndExcluding":"6.6.113"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.18","versionEndExcluding":"6.12.54"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.18","versionEndExcluding":"6.17.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.18","versionEndExcluding":"6.18"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2025-40201","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-15T21:58:02.275858Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-15T22:02:40.564Z"}}]}}}