CVE-2026-3904
MediumCVSS 6.2Exploitation Probability (EPSS)
Low risk4th percentile - higher than 4% of all known CVEs
Summary
In the GNU C Library version 2.36 on x86_64 systems, calling functions that use nscd caching may cause a crash. The issue stems from an optimized memcmp implementation that, when inputs are concurrently modified by other threads, can crash the nscd client and the application using it.
Risk Assessment
This vulnerability can cause applications using nscd to crash under high load, leading to service disruption and potential denial of service.
Recommendation
Update the GNU C Library to a version containing the fix. Distributions that have cherry-picked the memcmp SSE2 optimization should also apply the patch to prevent nscd client crashes.
Original NVD description (English source)
Calling NSS-backed functions that support caching via nscd may call the nscd client side code and in the GNU C Library version 2.36 under high load on x86_64 systems, the client may call memcmp on inputs that are concurrently modified by other processes or threads and crash. The nscd client in the GNU C Library uses the memcmp function with inputs that may be concurrently modified by another thread, potentially resulting in spurious cache misses, which in itself is not a security issue. However in the GNU C Library version 2.36 an optimized implementation of memcmp was introduced for x86_64 which could crash when invoked with such undefined behaviour, turning this into a potential crash of the nscd client and the application that uses it. This implementation was backported to the 2.35 branch, making the nscd client in that branch vulnerable as well. Subsequently, the fix for this issue was backported to all vulnerable branches in the GNU C Library repository. It is advised that distributions that may have cherry-picked the memcpy SSE2 optimization in their copy of the GNU C Library, also apply the fix to avoid the potential crash in the nscd client.