CVE-2025-21899
Estado: ModificadaMedia (5.5)—
In the Linux kernel, the following vulnerability has been resolved:
tracing: Fix bad hist from corrupting named_triggers list
The following commands causes a crash:
~# cd /sys/kernel/tracing/events/rcu/rcu_callback ~# echo 'hist:name=bad:keys=common_pid:onmax(bogus).save(common_pid)' > trigger bash: echo: write error: Invalid argument ~# echo 'hist:name=bad:keys=common_pid' > trigger
Because the following occurs:
The next time a hist with name is registered, it causes an u-a-f bug and the kernel can crash.
Move the code around such that if event_trigger_register() succeeds, the next thing called is hist_trigger_enable() which adds it to the list.
Leer descripción completaMostrar menos
A bunch of actions is called if get_named_trigger_data() returns false. But that doesn't need to be called after event_trigger_register(), so it can be moved up, allowing event_trigger_register() to be called just before hist_trigger_enable() keeping them together and allowing the file->triggers to be properly populated.
Detalles técnicos trazas, registros y código del informe original
event_trigger_write() {
trigger_process_regex() {
event_hist_trigger_parse() {
data = event_trigger_alloc(..);
event_trigger_register(.., data) {
cmd_ops->reg(.., data, ..) [hist_register_trigger()] {
data->ops->init() [event_hist_trigger_init()] {
save_named_trigger(name, data) {
list_add(&data->named_list, &named_triggers);
}
}
}
}
ret = create_actions(); (return -EINVAL)
if (ret)
goto out_unreg;
[..]
ret = hist_trigger_enable(data, ...) {
list_add_tail_rcu(&data->list, &file->triggers); <<<---- SKIPPED!!! (this is important!)
[..]
out_unreg:
event_hist_unregister(.., data) {
cmd_ops->unreg(.., data, ..) [hist_unregister_trigger()] {
list_for_each_entry(iter, &file->triggers, list) {
if (!hist_trigger_match(data, iter, named_data, false)) <- never matches
continue;
[..]
test = iter;
}
if (test && test->ops->free) <<<-- test is NULL
test->ops->free(test) [event_hist_trigger_free()] {
[..]
if (data->name)
del_named_trigger(data) {
list_del(&data->named_list); <<<<-- NEVER gets removed!
}
}
}
}
[..]
kfree(data); <<<-- frees item but it is still on listCVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Puntuación base: 5.5
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.21%
- Percentil entre todas las CVEs puntuadas: 11
- Fecha de la puntuación: 5/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
Tecnologías afectadas (1)
CWE
- CWE-476
Referencias
- https://git.kernel.org/stable/c/435d2964af815aae456db554c62963b4515f19d0
- https://git.kernel.org/stable/c/43b254d46c740bf9dbe65709afa021dd726dfa99
- https://git.kernel.org/stable/c/5ae1b18f05ee2b849dc03b6c15d7da0c1c6efa77
- https://git.kernel.org/stable/c/6f86bdeab633a56d5c6dccf1a2c5989b6a5e323e
- https://git.kernel.org/stable/c/f1ae50cfb818ce1ac7a674406dfadb7653e2552d
- https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html
JSON original (NVD)
Mostrar
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"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."
},
{
"lang": "es",
"value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: tracing: Fix bad hist from corrupting named_triggers list Los siguientes comandos provocan un bloqueo: ~# cd /sys/kernel/tracing/events/rcu/rcu_callback ~# echo 'hist:name=bad:keys=common_pid:onmax(bogus).save(common_pid)' > trigger bash: echo: error de escritura: argumento no válido ~# echo 'hist:name=bad:keys=common_pid' > trigger Porque ocurre lo siguiente: event_trigger_write() { trigger_process_regex() { event_hist_trigger_parse() { data = event_trigger_alloc(..); event_trigger_register(.., data) { cmd_ops->reg(.., data, ..) [hist_register_trigger()] { data->ops->init() [event_hist_trigger_init()] { save_named_trigger(name, data) { list_add(&data->named_list, &named_triggers); } } } } ret = create_actions(); (return -EINVAL) if (ret) goto out_unreg; [..] ret = hist_trigger_enable(data, ...) { list_add_tail_rcu(&data->list, &file->triggers); <<<---- ¡¡¡SALTAR!!! (¡esto es importante!) [..] out_unreg: event_hist_unregister(.., data) { cmd_ops->unreg(.., data, ..) [hist_unregister_trigger()] { list_for_each_entry(iter, &file->triggers, list) { if (!hist_trigger_match(data, iter, named_data, false)) <- never matches continue; [..] test = iter; } if (test && test->ops->free) <<<-- test is NULL test->ops->free(test) [event_hist_trigger_free()] { [..] if (data->name) del_named_trigger(data) { list_del(&data->named_list); <<<<-- ¡NUNCA se elimina! } } } } [..] kfree(datos); <<<-- libera el elemento, pero sigue en la lista. La próxima vez que se registre un hist con nombre, se producirá un error de uaf y el kernel podría bloquearse. Desplace el código de forma que, si event_trigger_register() tiene éxito, se llame a hist_trigger_enable(), lo que lo añade a la lista. Se invocan varias acciones si get_named_trigger_data() devuelve falso. Sin embargo, no es necesario llamarlo después de event_trigger_register(), por lo que se puede adelantar, lo que permite llamar a event_trigger_register() justo antes de hist_trigger_enable(), manteniéndolos juntos y permitiendo que los disparadores de archivo se rellenen correctamente."
}
],
"lastModified": "2026-07-30T06:21:56.000",
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