CVE-2026-53163: Linux kernel · locking/rtmutex: Skip remove_waiter() when waiter is not enqueued
Affects Linux kernelSource CVE Database V5
Not known to be exploited · fixed in bfbc047ceb42c0e1fac8f3a155d4548a8bbe76b1 : update Linux kernel when convenient.
Data as of 6 Nov 2026, 16:49 UTC
Rated by Threat Radar · No CVSS score from NVD or the CNA
Thin evidence
One scorer or none- CISA SSVC
- Exploitation
- No evidence of active exploitation and no public proof of concept
- Automatable
- Attackers cannot reliably automate steps 1–4 of the kill chain
- Technical impact
- Limited control over the software or limited information exposure
CISA SSVC assessment, 2026-11-06.
- Patch
- Available – fixed in bfbc047ceb42c0e1fac8f3a155d4548a8bbe76b1, a388e3dfaf9538a680de5ed43a8ebb5dd45b6e53, 55363fa0a04524d11efeaadee734d2db1756ed27 +10
Exploitation evidence
Disclosed: evidence found.
CVE published 25 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 6 Nov 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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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
- git.kernel.org/stable/c/bfbc047ceb42c0e1fac8f3a155d4548a8bbe76b1 (opens in a new tab)
- git.kernel.org/stable/c/4ffacf76a457b7ca8ac05f5df8740b0d8f53574a (opens in a new tab)
- git.kernel.org/stable/c/4afda3a1da02129568a3a2f1898aa13e6763bcba (opens in a new tab)
- git.kernel.org/stable/c/6707d7e0b71748cb3cd95bad81dae5fe1b3c8f48 (opens in a new tab)
- git.kernel.org/stable/c/5799f9bd7fee40370b93ab1ddf001cdc7017c14d (opens in a new tab)
- git.kernel.org/stable/c/a388e3dfaf9538a680de5ed43a8ebb5dd45b6e53 (opens in a new tab)
- git.kernel.org/stable/c/55363fa0a04524d11efeaadee734d2db1756ed27 (opens in a new tab)
- git.kernel.org/stable/c/40a25d59e85b3c8709ac2424d44f65610467871e (opens in a new tab)