Concurrent Access Crash Vulnerability in Linux Kernel's GCOV Instrumentation

CVE-2026-63825

What is CVE-2026-63825?

A vulnerability in the Linux kernel's GCOV instrumentation allows multiple CPUs to concurrently access global branch counters, leading to inconsistent values and potential out-of-bounds memory writes. This issue emerges during IPComp (IP Payload Compression) processing in the inflate_fast() function. The root cause is the merging of GCOV counters and loop induction variables, increasing the risk of crashes when accessed simultaneously by different CPUs. This flaw can manifest as a bug triggered by page faults when the GCOV counter is modified unexpectedly. Addressing this issue involves utilizing atomic counter updates to ensure safer concurrent access, thereby preventing the observed memory write exceptions.

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