CVE-2026-106452: yawkat LZ4 Java LZ4BlockInputStream Allocates An Unvalidated Compressed Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-4v53-57pg-c464",
  "modified" : "2026-10-07T16:17:51Z",
  "published" : "2026-10-07T16:17:50Z",
  "aliases" : [ "CVE-2026-106452" ],
  "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 < 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 >= 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 >= 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.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "at.yawk.lz4:lz4-java"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.11.2"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.11.1"
    }
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.lz4:lz4-java"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "1.8.1"
      } ]
    } ]
  } ],
  "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"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-789" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-07T16:17:50Z",
    "nvd_published_at" : "2026-10-06T20:17:27Z"
  }
}