Bug 2454320 (CVE-2026-23415)

Summary: CVE-2026-23415 kernel: futex: Fix UaF between futex_key_to_node_opt() and vma_replace_policy()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel. A timing issue, known as a race condition, exists within the futex subsystem. This vulnerability could allow a local attacker to access memory after it has been freed, leading to a system crash (denial of service) or potentially the disclosure of sensitive information.
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Description OSIDB Bzimport 2026-04-02 12:02:20 UTC 
In the Linux kernel, the following vulnerability has been resolved:

futex: Fix UaF between futex_key_to_node_opt() and vma_replace_policy()

During futex_key_to_node_opt() execution, vma->vm_policy is read under
speculative mmap lock and RCU. Concurrently, mbind() may call
vma_replace_policy() which frees the old mempolicy immediately via
kmem_cache_free().

This creates a race where __futex_key_to_node() dereferences a freed
mempolicy pointer, causing a use-after-free read of mpol->mode.

[  151.412631] BUG: KASAN: slab-use-after-free in __futex_key_to_node (kernel/futex/core.c:349)
[  151.414046] Read of size 2 at addr ffff888001c49634 by task e/87

[  151.415969] Call Trace:

[  151.416732]  __asan_load2 (mm/kasan/generic.c:271)
[  151.416777]  __futex_key_to_node (kernel/futex/core.c:349)
[  151.416822]  get_futex_key (kernel/futex/core.c:374 kernel/futex/core.c:386 kernel/futex/core.c:593)

Fix by adding rcu to __mpol_put().
Comment 1 Jon Moroney 2026-04-02 21:25:02 UTC Comment hidden (spam)
Comment 7 errata-xmlrpc 2026-08-06 09:14:49 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:51035 https://access.redhat.com/errata/RHSA-2026:51035
Comment 8 errata-xmlrpc 2026-08-11 08:55:22 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:53330 https://access.redhat.com/errata/RHSA-2026:53330