{"id":"GHSA-4v53-57pg-c464","summary":"yawkat LZ4 Java: LZ4BlockInputStream allocates an unvalidated compressed length from the stream header","details":"### Summary\n\n`LZ4BlockInputStream` grows its compressed-input buffer to the attacker-controlled `compressedLen` value from the legacy `LZ4Block` stream header before reading any payload bytes. A header-only input can therefore trigger a near-2 GiB allocation and exhaust the JVM heap.\n\n### Details\n\nIn `net.jpountz.lz4.LZ4BlockInputStream`, `refill()` validates that `compressedLen` is nonnegative but does not cap it before allocation:\n\n```java\ncase COMPRESSION_METHOD_LZ4:\n  if (compressedBuffer.length \u003c compressedLen) {\n    compressedBuffer = new byte[Math.max(compressedLen, compressedBuffer.length * 3 / 2)];\n  }\n  readFully(compressedBuffer, compressedLen);\n```\n\nThe paired `LZ4BlockOutputStream` never emits such a block. If compression is not smaller than the original block, it writes the block as RAW:\n\n```java\nif (compressedLength \u003e= o) {\n  compressMethod = COMPRESSION_METHOD_RAW;\n  compressedLength = o;\n} else {\n  compressMethod = COMPRESSION_METHOD_LZ4;\n}\n```\n\nExisting readers generally accept noncanonical LZ4-method blocks where `compressedLen \u003e= originalLen`, but no canonical writer found produces them.\n\n### Impact\n\nApplications that pass attacker-controlled legacy `LZ4Block` streams to `LZ4BlockInputStream` can suffer heap exhaustion from a header-only input. The impact is availability-only and requires no valid compressed payload.\n\n### Patch\n\nAs of lz4-java 1.11.2, lz4-java rejects lz4 blocks where the compressed length is larger than uncompressed. Readers would generally emit these as raw blocks instead. You can use the new `acceptOversizedBlocks` flag to restore the old behavior, but this reintroduces the DoS vector.","aliases":["CVE-2026-106452"],"modified":"2026-10-07T16:30:04.845963758Z","published":"2026-10-07T16:17:50Z","database_specific":{"github_reviewed":true,"github_reviewed_at":"2026-10-07T16:17:50Z","nvd_published_at":"2026-10-06T20:17:27Z","cwe_ids":["CWE-789"],"severity":"MODERATE"},"references":[{"type":"WEB","url":"https://github.com/yawkat/lz4-java/security/advisories/GHSA-4v53-57pg-c464"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-106452"},{"type":"WEB","url":"https://github.com/yawkat/lz4-java/commit/bb83dd16163cdb71231af06b0a5651881148a634"},{"type":"PACKAGE","url":"https://github.com/yawkat/lz4-java"},{"type":"WEB","url":"https://github.com/yawkat/lz4-java/releases/tag/v1.11.2"}],"affected":[{"package":{"name":"at.yawk.lz4:lz4-java","ecosystem":"Maven","purl":"pkg:maven/at.yawk.lz4/lz4-java"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.11.2"}]}],"versions":["1.10.0","1.10.1","1.10.2","1.10.3","1.10.4","1.11.0","1.11.1","1.8.1","1.9.0"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-4v53-57pg-c464/GHSA-4v53-57pg-c464.json","last_known_affected_version_range":"\u003c= 1.11.1"}},{"package":{"name":"org.lz4:lz4-java","ecosystem":"Maven","purl":"pkg:maven/org.lz4/lz4-java"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"1.8.1"}]}],"versions":["1.4","1.4.0","1.4.1","1.5.0","1.5.1","1.6.0","1.7.0","1.7.1","1.8.0","1.8.1"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-4v53-57pg-c464/GHSA-4v53-57pg-c464.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"}]}