CVE-2026-43499

In the Linux kernel, the following vulnerability has been resolved:

rtmutex: Use waiter::task instead of current in remove_waiter()

remove_waiter() is used by the slowlock paths, but it is also used for proxy-lock rollback in rt_mutex_start_proxy_lock() when invoked from futex_requeue().

In the latter case waiter::task is not current, but remove_waiter() operates on current for the dequeue operation. That results in several problems:

1. the rbtree dequeue happens without waiter::task::pi_lock being held

2. the waiter tasks pi_blocked_on state is not cleared, which leaves a dangling pointer primed for UAF around.

3. rt_mutex_adjust_prio_chain() operates on the wrong top priority waiter task

Use waiter::task instead of current in all related operations in remove_waiter() to cure those problems.

[ tglx: Fixup rt_mutex_adjust_prio_chain(), add a comment and amend the changelog ]

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/3bfdc63936dd4773109b7b8c280c0f3b5ae7d349
• https://git.kernel.org/stable/c/3fb7394a837740770f0d6b4b30567e60786a63f2
• https://git.kernel.org/stable/c/6d52dfcb2a5db86e346cf51f8fcf2071b8085166
• https://git.kernel.org/stable/c/88614876370aac8ad1050ad785a4c095ba17ac11
• https://git.kernel.org/stable/c/8a1fc8d698ac5e5916e3082a0f74450d71f9611f
• https://git.kernel.org/stable/c/d8cce4773c2b23d819baf5abedc62f7b430e8745
• http://www.openwall.com/lists/oss-security/2026/07/08/12