Medium 5.5Published Jun 25, 2026

CVE-2026-53163locking/rtmutex: Skip remove_waiter() when waiter is not enqueued

Updated under an hour ago (Oct 27, 2026, 8:50 PM ET)

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Exploited in the last 30 days

In the Linux kernel, the following vulnerability has been resolved: locking/rtmutex: Skip remove_waiter() when waiter is not enqueued syzbot triggered the following splat in remove_waiter() via FUTEX_CMP_REQUEUE_PI: KASAN: null-ptr-deref in range [0x0000000000000a88-0x0000000000000a8f] class_raw_spinlock_constructor remove_waiter+0x159/0x1200 kernel/locking/rtmutex.c:1561 rt_mutex_start_proxy_lock+0x103/0x120 futex_requeue+0x10e4/0x20d0 __x64_sys_futex+0x34f/0x4d0 task_blocks_on_rt_mutex() does not arm the waiter upon deadlock detection, leaving waiter->task nil, where 3bfdc63936dd ("rtmutex: Use waiter::task instead of current in remove_waiter()") made this fatal. Furthermore, rt_mutex_start_proxy_lock() should not be calling into remove_waiter() upon a successfully grabbing the rtmutex. 1a1fb985f2e2 ("futex: Handle early deadlock return correctly"), moved the remove_waiter() out of __rt_mutex_start_proxy_lock() (where 'ret' was only ever 0 or < 0) into the wrapper. Tighten this check to account for try_to_take_rt_mutex().

CVSS: 5.5 MEDIUM (v3.1, NVD)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): Not given
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Linux
NVD analysis: Modified
Record last updated: Jul 24, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Linux Linux linux:linux (from the name)	from f3fa3424bceb128d2be4b3745506b22844b87db7 before bfbc047ceb42c0e1fac8f3a155d4548a8bbe76b1; 838ce5cb5d93c3ab8b27e75bc6ad905a94b752fd builds before 4ffacf76a457b7ca8ac05f5df8740b0d8f53574a; from d8cce4773c2b23d819baf5abedc62f7b430e8745 before 4afda3a1da02129568a3a2f1898aa13e6763bcba; from 8a1fc8d698ac5e5916e3082a0f74450d71f9611f before 6707d7e0b71748cb3cd95bad81dae5fe1b3c8f48; from 6d52dfcb2a5db86e346cf51f8fcf2071b8085166 before 5799f9bd7fee40370b93ab1ddf001cdc7017c14d; from 3fb7394a837740770f0d6b4b30567e60786a63f2 before a388e3dfaf9538a680de5ed43a8ebb5dd45b6e53; 88614876370aac8ad1050ad785a4c095ba17ac11 builds before 55363fa0a04524d11efeaadee734d2db1756ed27; from 3bfdc63936dd4773109b7b8c280c0f3b5ae7d349 before 40a25d59e85b3c8709ac2424d44f65610467871e	CNA record
linux linux_kernel linux:linux_kernel	from 6.1.175 before 6.1.177; from 6.6.140 before 6.6.144; from 6.12.86 before 6.12.95; from 6.18.27 before 6.18.36; from 7.0.4 before 7.0.13; 7.1; 7.1; 7.1; and 3 more ranges	NVD

References

References

https://git.kernel.org/stable/c/bfbc047ceb42c0e1fac8f3a155d4548a8bbe76b1
https://git.kernel.org/stable/c/4ffacf76a457b7ca8ac05f5df8740b0d8f53574a
https://git.kernel.org/stable/c/4afda3a1da02129568a3a2f1898aa13e6763bcba	patch
https://git.kernel.org/stable/c/6707d7e0b71748cb3cd95bad81dae5fe1b3c8f48	patch
https://git.kernel.org/stable/c/5799f9bd7fee40370b93ab1ddf001cdc7017c14d	patch
https://git.kernel.org/stable/c/a388e3dfaf9538a680de5ed43a8ebb5dd45b6e53	patch
https://git.kernel.org/stable/c/55363fa0a04524d11efeaadee734d2db1756ed27	patch
https://git.kernel.org/stable/c/40a25d59e85b3c8709ac2424d44f65610467871e	patch

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.