CVE-2026-42587: Netty: HttpContentDecompressor maxAllocation bypass via Content-Encoding: br/zstd/snappy enables decompression bomb DoS

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

• netty nettybefore 4.1.133
• netty netty4.2.0 and later · before 4.2.13

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

• io.netty netty-codec-http

  • >= 4.2.0.Alpha1, < 4.2.13.Final, < 4.1.133.Finalaffected

• io.netty netty-codec-http2

  • >= 4.2.0.Alpha1, < 4.2.13.Final, < 4.1.133.Finalaffected

• netty netty

  • >= 4.2.0.Alpha1, < 4.2.13.Final, < 4.1.133.Finalaffected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Other highest-scoring records for the same primary product.

• CVE-2026-47691Netty has Insufficient Bailiwick Validation for NS Records
  40Plan
• CVE-2026-45674Netty Vulnerable to DNS Cache Poisoning via Missing Bailiwick Checks in CNAME Records
  40Plan
• CVE-2019-20445HttpObjectDecoder.java in Netty before 4.1.44 allows a Content-Length header to be accompanied by a second Content-Length header, or by a Tr
  40Plan

Published before and after this one in the same product

• ← EarlierCVE-2026-42585May 13, 2026 · Netty: HTTP Request Smuggling due to malformed Transfer-Encoding
  30Monitor
• ← EarlierCVE-2026-42586May 13, 2026 · Netty: CRLF Injection in Netty Redis Codec Encoder
  28Monitor
• Later →CVE-2026-44248May 13, 2026 · Netty: Resource exhaustion in MqttDecoder
  30Monitor

Root cause

Code that parses nested structures sets no depth or size limit. A small input can turn into a disproportionate processing load.

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

1function expand(node) {2  return node.children.map(expand);3}

1const MAX_DEPTH = 32;2function expand(node, depth = 0) {3  if (depth > MAX_DEPTH) throw new Error("too deep");4  return node.children.map((c) => expand(c, depth + 1));5}

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.