CVE-2026-64560 Detail
Description
In the Linux kernel, the following vulnerability has been resolved: posix-cpu-timers: Prevent UAF caused by non-leader exec() race Wongi and Jungwoo decoded and reported a non-leader exec() related race which can result in an UAF: sys_timer_delete() exec() posix_cpu_timer_del() // Observes old leader p = pid_task(pid, pid_type); de_thread() switch_leader(); release_task(old_leader) __exit_signal(old_leader) sighand = lock(old_leader, sighand); posix_cpu_timers*_exit(); sighand = lock_task_sighand(p) unhash_task(old_leader); sh = lock(p, sighand) old_leader->sighand = NULL; unlock(sighand); (p->sighand == NULL) unlock(sh) return NULL; // Returns without action if(!sighand) return 0; free_posix_timer(); This is "harmless" unless the deleted timer was armed and enqueued in p->signal because on exec() a TGID targeted timer is inherited. As sys_timer_delete() freed the underlying posix timer object run_posix_cpu_timers() or any timerqueue related add/delete operations on other timers will access the freed object's timerqueue node, which results in an UAF. There is a similar problem vs. posix_cpu_timer_set(). For regular posix timers it just transiently returns -ESRCH to user space, but for the use case in do_cpu_nanosleep() it's the same UAF just that the k_itimer is allocated on the stack. Also posix_cpu_timer_rearm() fails to rearm the timer, which means it stops to expire. While debating solutions Frederic pointed out another problem: posix_cpu_timer_del(tmr) __exit_signal(p) posix_cpu_timers*_exit(p); unhash_task(p); p->sighand = NULL; sh = lock_task_sighand(p) sighand = p->sighand; if (!sighand) return NULL; lock(sighand); if (!sh) WARN_ON_ONCE(timer_queued(tmr)); On weakly ordered architectures it is not guaranteed that posix_cpu_timer_del() will observe the stores in posix_cpu_timers*_exit() when p->sighand is observed as NULL, which means the WARN() can be a false positive. Solve these issues by: 1) Changing the store in __exit_signal() to smp_store_release(). 2) Adding a smp_acquire__after_ctrl_dep() into the !sighand path of lock_task_sighand(). 3) Creating a helper function for looking up the task and locking sighand which does not return when sighand == NULL. Instead it retries the task lookup and only if that fails it gives up. 4) Using that helper in the three affected functions. #1/#2 ensures that the reader side which observes sighand == NULL also observes all preceeding stores, i.e. the stores in posix_cpu_timers*_exit() and the ones in unhash_task(). #3 ensures that the above described non-leader exec() situation is handled gracefully. When the task lookup returns the old leader, but sighand == NULL then it retries. In the non-leader exec() case the subsequent task lookup will observe the new leader due to #1/#2. In normal exit() scenarios the subsequent lookup fails. When the task lookup fails, the function also checks whether the timer is still enqueued and issues a warning if that's the case. Unfortunately there is nothing which can be done about it, but as the task is already not longer visible the timer should not be accessed anymore. This check also requires memory ordering, which is not provided when the first lookup fails. To achieve that the check is preceeded by a smp_rmb() which pairs with the smp_wmb() in write_seqlock() in __exit_signal(). That ensures that the stores in posix_cpu_timers*_exit() are visible. The history of the non-leader exec() issue goes back to the early days of posix CPU timers, which stored a pointer to the group leader task in the timer. That obviously fails when a non-leader exec() switches the leader. commit e0a70217107e ("posix-cpu-timers: workaround to suppress the problems with mt exec") added a temporary workaround for that in 2010 which surv ---truncated---
Metrics
NVD enrichment efforts reference publicly available information to associate vector strings. CVSS information contributed by other sources is also displayed.
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
CVSS 2.0 Severity and Vector Strings:
References to Advisories, Solutions, and Tools
By selecting these links, you will be leaving NIST webspace. We have provided these links to other web sites because they may have information that would be of interest to you. No inferences should be drawn on account of other sites being referenced, or not, from this page. There may be other web sites that are more appropriate for your purpose. NIST does not necessarily endorse the views expressed, or concur with the facts presented on these sites. Further, NIST does not endorse any commercial products that may be mentioned on these sites. Please address comments about this page to [email protected].
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|
Change History
3 change records found show changes
CVE Modified by kernel.org 7/30/2026 8:19:03 AM
| Action | Type | Old Value | New Value |
|---|---|---|---|
| Added | Reference |
https://git.kernel.org/stable/c/12a891c773aeb5823d63dbd0cb2ab931d6c21c9b |
|
| Added | Reference |
https://git.kernel.org/stable/c/67aa823e3e8c229c6d374df79c804f6721cb83b6 |
|
| Added | Reference |
https://git.kernel.org/stable/c/6a7ecc25abe6f0fecc6e62a05096987200edbd02 |
|
| Added | Reference |
https://git.kernel.org/stable/c/cc35ddbc497311e0b6b9a6a6a4f4d1217d6ab1aa |
|
| Added | Reference |
https://git.kernel.org/stable/c/d8bcb28abad857f1415da7656f19b2ada90af04f |
|
| Added | Reference |
https://git.kernel.org/stable/c/e74443f5db0037c556ef436fa64b88bf4ea08f83 |
|
| Changed | Affected |
[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","programFiles":["kernel/exit.c","kernel/signal.c","kernel/time/posix-cpu-timers.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","versions":[{"version":"55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59","lessThan":"ad1cafa1bdaa71da85d71cac053838bbe97852b6","versionType":"git","status":"affected"},{"version":"55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59","lessThan":"920f893f735e92ba3a1cd9256899a186b161928d","versionType":"git","status":"affected"}]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","programFiles":["kernel/exit.c","kernel/signal.c","kernel/time/posix-cpu-timers.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","versions":[{"version":"5.7","status":"affected"},{"version":"0","lessThan":"5.7","versionType":"semver","status":"unaffected"},{"version":"7.1.5","lessThanOrEqual":"7.1.*","versionType":"semver","status":"unaffected"},{"version":"7.2-rc3","lessThanOrEqual":"*","versionType":"original_commit_for_fix","status":"unaffected"}]}]
|
Record truncated, showing 2048 of 2543 characters.
View Entire Change Record [{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","programFiles":["kernel/exit.c","kernel/signal.c","kernel/time/posix-cpu-timers.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","versions":[{"version":"55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59","lessThan":"67aa823e3e8c229c6d374df79c804f6721cb83b6","versionType":"git","status":"affected"},{"version":"55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59","lessThan":"d8bcb28abad857f1415da7656f19b2ada90af04f","versionType":"git","status":"affected"},{"version":"55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59","lessThan":"cc35ddbc497311e0b6b9a6a6a4f4d1217d6ab1aa","versionType":"git","status":"affected"},{"version":"55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59","lessThan":"12a891c773aeb5823d63dbd0cb2ab931d6c21c9b","versionType":"git","status":"affected"},{"version":"55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59","lessThan":"e74443f5db0037c556ef436fa64b88bf4ea08f83","versionType":"git","status":"affected"},{"version":"55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59","lessThan":"6a7ecc25abe6f0fecc6e62a05096987200edbd02","versionType":"git","status":"affected"},{"version":"55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59","lessThan":"ad1cafa1bdaa71da85d71cac053838bbe97852b6","versionType":"git","status":"affected"},{"version":"55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59","lessThan":"920f893f735e92ba3a1cd9256899a186b161928d","versionType":"git","status":"affected"}]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","programFiles":["kernel/exit.c","kernel/signal.c","kernel/time/posix-cpu-timers.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","versions":[{"version":"5.7","status":"affected"},{"version":"0","lessThan":"5.7","versionType":"semver","status":"unaffected"},{"version":"5.10.262","lessThanOrEqual":"5.10.*","versionType":"semver","status":"unaffected"},{"version":"5.15.213","lessThanOrEqual":"5.15.*","versionType":"semver","status":"unaffected"},{"version":"6.1.180","lessThanOrEqual":"6.1.*","versionType":"semver","status":
|
CVE Modified by kernel.org 7/30/2026 2:25:59 AM
| Action | Type | Old Value | New Value |
|---|---|---|---|
| Added | CVSS V3.1 |
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
New CVE Received from kernel.org 7/29/2026 1:16:53 PM
| Action | Type | Old Value | New Value |
|---|---|---|---|
| Added | Description |
Record truncated, showing 2048 of 3998 characters.
View Entire Change Record In the Linux kernel, the following vulnerability has been resolved:
posix-cpu-timers: Prevent UAF caused by non-leader exec() race
Wongi and Jungwoo decoded and reported a non-leader exec() related race
which can result in an UAF:
sys_timer_delete() exec()
posix_cpu_timer_del()
// Observes old leader
p = pid_task(pid, pid_type); de_thread()
switch_leader();
release_task(old_leader)
__exit_signal(old_leader)
sighand = lock(old_leader, sighand);
posix_cpu_timers*_exit();
sighand = lock_task_sighand(p) unhash_task(old_leader);
sh = lock(p, sighand) old_leader->sighand = NULL;
unlock(sighand);
(p->sighand == NULL)
unlock(sh)
return NULL;
// Returns without action
if(!sighand)
return 0;
free_posix_timer();
This is "harmless" unless the deleted timer was armed and enqueued in
p->signal because on exec() a TGID targeted timer is inherited.
As sys_timer_delete() freed the underlying posix timer object
run_posix_cpu_timers() or any timerqueue related add/delete operations on
other timers will access the freed object's timerqueue node, which results
in an UAF.
There is a similar problem vs. posix_cpu_timer_set(). For regular posix
timers it just transiently returns -ESRCH to user space, but for the use
case in do_cpu_nanosleep() it's the same UAF just that the k_itimer is
allocated on the stack.
Also posix_cpu_timer_rearm() fails to rearm the timer, which means it stops
to expire.
While debating solutions Frederic pointed out another problem:
posix_cpu_timer_del(tmr)
__exit_signal(p)
posix_cpu_timers*_exit(p);
unhash_task(p);
p->sighand = NULL;
sh = lock_task_sighand(p)
sighand = p->sighand;
if (!sighand)
return NULL;
lock(sighand);
if (!sh)
WARN_ON_ONCE(timer_queued(tmr));
On weakly ordered architectures it is not guaranteed that
posix_cpu_timer_del() will observe the stores in posix_cpu_timers*_exit()
when p->sighand is observed as NULL,
|
|
| Added | Reference |
https://git.kernel.org/stable/c/920f893f735e92ba3a1cd9256899a186b161928d |
|
| Added | Reference |
https://git.kernel.org/stable/c/ad1cafa1bdaa71da85d71cac053838bbe97852b6 |
|
| Added | Affected |
[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","programFiles":["kernel/exit.c","kernel/signal.c","kernel/time/posix-cpu-timers.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","versions":[{"version":"55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59","lessThan":"ad1cafa1bdaa71da85d71cac053838bbe97852b6","versionType":"git","status":"affected"},{"version":"55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59","lessThan":"920f893f735e92ba3a1cd9256899a186b161928d","versionType":"git","status":"affected"}]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","programFiles":["kernel/exit.c","kernel/signal.c","kernel/time/posix-cpu-timers.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","versions":[{"version":"5.7","status":"affected"},{"version":"0","lessThan":"5.7","versionType":"semver","status":"unaffected"},{"version":"7.1.5","lessThanOrEqual":"7.1.*","versionType":"semver","status":"unaffected"},{"version":"7.2-rc3","lessThanOrEqual":"*","versionType":"original_commit_for_fix","status":"unaffected"}]}]
|
Quick Info
CVE Dictionary Entry:
CVE-2026-64560
NVD
Published Date:
07/29/2026
NVD
Last Modified:
07/30/2026
Source:
kernel.org