Medium · published October 7, 2026
yawkat LZ4 Java provides LZ4 compression for Java. Prior to 1.11.2, net.jpountz.lz4.LZ4BlockInputStream refill() validates that the compressedLen field in a legacy LZ4Block header is nonnegative but allocates a compressed-input buffer of that attacker-controlled size before reading payload data, allowing a header-only stream to request a near-2 GiB allocation and exhaust the JVM heap. Canonical writers emit raw blocks when compression is not smaller than the original block, but vulnerable readers accept non-canonical oversized compressed blocks. This issue is fixed in version 1.11.2.