CVE-2026-23415 Linux CVE debrief

Who should care

Linux kernel developers, administrators, and users who need to ensure the security and stability of their Linux systems, particularly those with low attack complexity and high impact, should take priority in applying patches or updates to vulnerable systems. Those responsible for Linux kernel maintenance, vulnerability management, and security teams should review and update Linux kernel versions to ensure fixes are applied.

Why it matters

This vulnerability has a high CVSS score of 7.8 and can lead to a use-after-free read of `mpol->mode`, potentially causing system crashes or security issues. Linux kernel developers, administrators, and users should take priority in applying patches or updates to vulnerable systems.

• Verify Linux kernel versions and apply patches to prevent potential use-after-free reads
• Monitor Linux kernel updates and patches for potential vulnerabilities
• Assess exposure of Linux systems to this vulnerability

Technical summary

The Linux kernel's futex subsystem has a use-after-free vulnerability due to a race condition between `futex_key_to_node_opt()` and `vma_replace_policy()`. This can lead to a use-after-free read of `mpol->mode`. The vulnerability has been resolved by adding RCU to `__mpol_put()`. The use-after-free read of `mpol->mode` can occur when `vma_replace_policy()` frees the old mempolicy immediately via `kmem_cache_free()`. The vulnerability was introduced due to a race condition between `futex_key_to_node_opt()` and `vma_replace_policy()`.

Defensive priority

Apply patches or updates from the Linux vendor to vulnerable systems, particularly those with low attack complexity and high impact.

Recommended defensive actions

• Apply patches or updates from the Linux vendor to vulnerable systems
• Review and update Linux kernel versions to ensure fixes are applied
• Monitor Linux kernel updates and patches for potential vulnerabilities
• Verify Linux kernel versions and apply patches to prevent potential use-after-free reads
• Assess exposure of Linux systems to this vulnerability
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.

Evidence notes

The vulnerability was introduced due to a race condition between `futex_key_to_node_opt()` and `vma_replace_policy()`. The use-after-free read of `mpol->mode` can occur when `vma_replace_policy()` frees the old mempolicy immediately via `kmem_cache_free()`.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.