Incorrect Synchronization Affecting kernel-devel package, versions *
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-CENTOS10-KERNELDEVEL-16929958
- published28 May 2026
- disclosed27 May 2026
Introduced: 27 May 2026
NewCVE-2026-46063 (opens in a new tab)How to fix?
There is no fixed version for Centos:10 kernel-devel.
NVD Description
Note: Versions mentioned in the description apply only to the upstream kernel-devel package and not the kernel-devel package as distributed by Centos.
See How to fix? for Centos:10 relevant fixed versions and status.
In the Linux kernel, the following vulnerability has been resolved:
x86/shstk: Prevent deadlock during shstk sigreturn
During sigreturn the shadow stack signal frame is popped. The kernel does this by reading the shadow stack using normal read accesses. When it can't assume the memory is shadow stack, it takes extra steps to makes sure it is reading actual shadow stack memory and not other normal readable memory. It does this by holding the mmap read lock while doing the access and checking the flags of the VMA.
Unfortunately that is not safe. If the read of the shadow stack sigframe hits a page fault, the fault handler will try to recursively grab another mmap read lock. This normally works ok, but if a writer on another CPU is also waiting, the second read lock could fail and cause a deadlock.
Fix this by not holding mmap lock during the read access to userspace.
Instead use mmap_lock_speculate_...() to watch for changes between dropping mmap lock and the userspace access. Retry if anything grabbed an mmap write lock in between and could have changed the VMA.
These mmap_lock_speculate_...() helpers use mm::mm_lock_seq, which is only available when PER_VMA_LOCK is configured. So make X86_USER_SHADOW_STACK depend on it. On x86, PER_VMA_LOCK is a default configuration for SMP kernels. So drop support for the other configs under the assumption that the !SMP shadow stack user base does not exist.
Currently there is a check that skips the lookup work when the SSP can be assumed to be on a shadow stack. While reorganizing the function, remove the optimization to make the tricky code flows more common, such that issues like this cannot escape detection for so long.
References
- https://bugzilla.redhat.com/show_bug.cgi?id=2481999
- https://access.redhat.com/security/cve/CVE-2026-46063
- https://git.kernel.org/stable/c/3d29db827502067626062f5c74dd502d14ab15bc
- https://git.kernel.org/stable/c/4f3374c990fb2adec06d20fd6d780927811c9aa0
- https://git.kernel.org/stable/c/9874b2917b9fbc30956fee209d3c4aa47201c64e
- https://git.kernel.org/stable/c/d042d69b417515959e49021fef008c9b04a99bd5
- https://git.kernel.org/stable/c/e2c2b044458cbf22da05264fa707308e8d4f86f9