CVE-2026-87824zstd-jni before 1.5.7-14 fails to validate the samples buffer capacity in Zstd.trainFromBufferDirect, allowing attackers to read past buffer boundaries by supplying oversized per-sample lengths. Attackers can trigger out-of-bounds memory access by providing crafted sample length arrays that cause the native implementation to walk past the buffer allocation, resulting in JVM termination.