{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-21899","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2024-12-29T08:45:45.783Z","datePublished":"2025-04-01T15:26:50.791Z","dateUpdated":"2026-08-05T11:55:14.373Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T11:55:14.373Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Fix bad hist from corrupting named_triggers list\n\nThe following commands causes a crash:\n\n ~# cd /sys/kernel/tracing/events/rcu/rcu_callback\n ~# echo 'hist:name=bad:keys=common_pid:onmax(bogus).save(common_pid)' > trigger\n bash: echo: write error: Invalid argument\n ~# echo 'hist:name=bad:keys=common_pid' > trigger\n\nBecause the following occurs:\n\nevent_trigger_write() {\n  trigger_process_regex() {\n    event_hist_trigger_parse() {\n\n      data = event_trigger_alloc(..);\n\n      event_trigger_register(.., data) {\n        cmd_ops->reg(.., data, ..) [hist_register_trigger()] {\n          data->ops->init() [event_hist_trigger_init()] {\n            save_named_trigger(name, data) {\n              list_add(&data->named_list, &named_triggers);\n            }\n          }\n        }\n      }\n\n      ret = create_actions(); (return -EINVAL)\n      if (ret)\n        goto out_unreg;\n[..]\n      ret = hist_trigger_enable(data, ...) {\n        list_add_tail_rcu(&data->list, &file->triggers); <<<---- SKIPPED!!! (this is important!)\n[..]\n out_unreg:\n      event_hist_unregister(.., data) {\n        cmd_ops->unreg(.., data, ..) [hist_unregister_trigger()] {\n          list_for_each_entry(iter, &file->triggers, list) {\n            if (!hist_trigger_match(data, iter, named_data, false))   <- never matches\n                continue;\n            [..]\n            test = iter;\n          }\n          if (test && test->ops->free) <<<-- test is NULL\n\n            test->ops->free(test) [event_hist_trigger_free()] {\n              [..]\n              if (data->name)\n                del_named_trigger(data) {\n                  list_del(&data->named_list);  <<<<-- NEVER gets removed!\n                }\n              }\n           }\n         }\n\n         [..]\n         kfree(data); <<<-- frees item but it is still on list\n\nThe next time a hist with name is registered, it causes an u-a-f bug and\nthe kernel can crash.\n\nMove the code around such that if event_trigger_register() succeeds, the\nnext thing called is hist_trigger_enable() which adds it to the list.\n\nA bunch of actions is called if get_named_trigger_data() returns false.\nBut that doesn't need to be called after event_trigger_register(), so it\ncan be moved up, allowing event_trigger_register() to be called just\nbefore hist_trigger_enable() keeping them together and allowing the\nfile->triggers to be properly populated."}],"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 only by writing a hist trigger command to a tracefs file (`/sys/kernel/tracing/events/*/trigger`) via the write(2) syscall. There is no network or remote data path into `event_hist_trigger_parse()`.\nAC:L - Triggering is fully deterministic — one failing `hist:name=bad:...onmax(bogus)...` write leaves the freed object linked in the global `named_triggers` list, and a second `hist:name=bad` write dereferences it; no race and no uncontrollable preconditions. `CONFIG_HIST_TRIGGERS=y` is standard in mainstream distro and Android kernels, and slab reclaim of the freed `event_trigger_data` is attacker-influenced via ordinary heap spraying.\nPR:L - No capability check exists on the code path; access is gated purely by tracefs file permissions, and tracefs is routinely delegated to a non-root tracing/shell group (Android shell, ChromeOS debugd, perf/tracing groups) via the `gid=` mount option. A local unprivileged user with that ordinary tracing access can execute the full sequence.\nUI:N - The attacker performs both writes themselves; no victim action or cooperation is needed at any point.\nS:U - The use-after-free and list corruption occur in kernel memory within the same security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - `find_named_trigger()` and `hist_trigger_match()` dereference the freed object's `name` and `private_data` pointers, so after reclaiming the slab object the attacker controls those pointers and obtains an arbitrary kernel-memory read primitive, plus leakage of the `named_triggers` list-head address.\nI:H - The freed object remains on a global list, so subsequent `list_add`/`list_del` operations write through attacker-controlled `named_list` pointers, and `data->private_data = named_data->private_data` produces type confusion into `hist_trigger_data` — a classic UAF write primitive usable for control-flow hijack.\nA:H - As stated in the commit, the second named-hist registration causes a use-after-free that crashes the kernel; list corruption reliably produces an oops or panic, denying service to the whole system."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/trace/trace_events_hist.c"],"versions":[{"version":"067fe038e70f6e64960d26a79c4df5f1413d0f13","lessThan":"5ae1b18f05ee2b849dc03b6c15d7da0c1c6efa77","status":"affected","versionType":"git"},{"version":"067fe038e70f6e64960d26a79c4df5f1413d0f13","lessThan":"43b254d46c740bf9dbe65709afa021dd726dfa99","status":"affected","versionType":"git"},{"version":"067fe038e70f6e64960d26a79c4df5f1413d0f13","lessThan":"435d2964af815aae456db554c62963b4515f19d0","status":"affected","versionType":"git"},{"version":"067fe038e70f6e64960d26a79c4df5f1413d0f13","lessThan":"f1ae50cfb818ce1ac7a674406dfadb7653e2552d","status":"affected","versionType":"git"},{"version":"067fe038e70f6e64960d26a79c4df5f1413d0f13","lessThan":"6f86bdeab633a56d5c6dccf1a2c5989b6a5e323e","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/trace/trace_events_hist.c"],"versions":[{"version":"4.17","status":"affected"},{"version":"0","lessThan":"4.17","status":"unaffected","versionType":"semver"},{"version":"6.1.130","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.81","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.18","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.13.6","lessThanOrEqual":"6.13.*","status":"unaffected","versionType":"semver"},{"version":"6.14","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.17","versionEndExcluding":"6.1.130"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.17","versionEndExcluding":"6.6.81"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.17","versionEndExcluding":"6.12.18"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.17","versionEndExcluding":"6.13.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.17","versionEndExcluding":"6.14"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/5ae1b18f05ee2b849dc03b6c15d7da0c1c6efa77"},{"url":"https://git.kernel.org/stable/c/43b254d46c740bf9dbe65709afa021dd726dfa99"},{"url":"https://git.kernel.org/stable/c/435d2964af815aae456db554c62963b4515f19d0"},{"url":"https://git.kernel.org/stable/c/f1ae50cfb818ce1ac7a674406dfadb7653e2552d"},{"url":"https://git.kernel.org/stable/c/6f86bdeab633a56d5c6dccf1a2c5989b6a5e323e"}],"title":"tracing: Fix bad hist from corrupting named_triggers list","x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CVE Program Container","references":[{"url":"https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html"}],"providerMetadata":{"orgId":"af854a3a-2127-422b-91ae-364da2661108","shortName":"CVE","dateUpdated":"2025-11-03T19:38:45.924Z"}}]}}