CVE-2026-99218

A flaw was found in the Linux kernel's core dump subsystem. A local user can trigger a race condition during process core dump creation when releasing parked threads without proper synchronization. This issue allows the kernel to access memory after it has been freed, which could enable an attacker to achieve privilege escalation or cause a Denial of Service (DoS) via a system crash.

This vulnerability is rated as having a Moderate impact rather than Important because exploitation requires local access and depends on winning an intricate timing window during task exit preemption. Although core dumping facilities are present in standard Red Hat Enterprise Linux deployments, an unprivileged attacker cannot trigger the race condition remotely. While memory corruption could theoretically allow local privilege elevation, the most probable outcome of an exploit attempt is an immediate kernel crash resulting in a denial of service.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

--- CME Mitigation Guidance (2026-11-04) --- Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure.

The highest-value action is to protect parked thread release in coredump_finish with RCU so task structures are not freed before wake_up_process executes: upgrade to the corresponding fixed Red Hat builds, which hold an RCU read lock across the loop releasing parked threads in coredump_finish, closing multithreaded core dump execution racing task preemption and exit. Until patched, this is only a concern on Linux systems where local unprivileged users can trigger core dumps of multithreaded processes — Non-Linux platforms and remote network access vectors are unaffected — so Restrict process core dump creation for unprivileged local accounts via ulimit or sysctl kernel.core_pattern configurations. As a compensating measure, Enable runtime memory error detection such as KASAN to trap task memory use-after-free conditions in try_to_wake_up during thread exit. These controls limit blast radius and contain exploitation, but they do not fix the underlying use-after-free race condition defect — apply the upstream patch to fully remediate.

Highest-impact CME: CME-1005 Runtime Memory Error Detection (KASAN/HWASan) (medium)