CVE-2026-53163: Linux kernel · locking/rtmutex: Skip remove_waiter() when waiter is not enqueued
Source GCVE Database
Not known to be exploited · CVSS 5.5 Medium.
Data as of 26 Oct 2026, 14:05 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 2% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 25 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
AI-suggested
Since this is a Linux kernel vulnerability, monitor official Linux kernel mailing lists and vendor advisories for patches addressing CVE-2026-53163. Apply official kernel updates once available to remediate this issue.
Description
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().
References
- nvd.nist.gov/vuln/detail/CVE-2026-53163 (opens in a new tab)
- git.kernel.org/stable/c/40a25d59e85b3c8709ac2424d44f65610467871e (opens in a new tab)
- git.kernel.org/stable/c/4afda3a1da02129568a3a2f1898aa13e6763bcba (opens in a new tab)
- git.kernel.org/stable/c/55363fa0a04524d11efeaadee734d2db1756ed27 (opens in a new tab)
- git.kernel.org/stable/c/5799f9bd7fee40370b93ab1ddf001cdc7017c14d (opens in a new tab)
- git.kernel.org/stable/c/6707d7e0b71748cb3cd95bad81dae5fe1b3c8f48 (opens in a new tab)
- git.kernel.org/stable/c/a388e3dfaf9538a680de5ed43a8ebb5dd45b6e53 (opens in a new tab)