Excessive CPU usage when URI template matcher is configured using regex in Envoy

Affected versions

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

• envoyproxy envoy1.26.0 and later · before 1.26.7
• envoyproxy envoy1.27.0 and later · before 1.27.3
• envoyproxy envoy1.28.0 and later · before 1.28.1
• envoyproxy envoy1.29.0 and later · before 1.29.1

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.

• envoyproxy envoy

  • >= 1.29.0, < 1.29.1, >= 1.28.0, < 1.28.1, >= 1.27.0, < 1.27.3, < 1.26.7affected

Other highest-scoring records for the same primary product.

• CVE-2024-30255HTTP/2: CPU exhaustion due to CONTINUATION frame flood
  56Plan
• CVE-2024-27919HTTP/2: memory exhaustion due to CONTINUATION frame flood
  56Plan
• CVE-2021-29492Bypass of path matching rules using escaped slash characters
  53Plan
• CVE-2019-15226Upon receiving each incoming request header data, Envoy will iterate over existing request headers to verify that the total size of the head
  49Plan
• CVE-2019-9901Envoy 1.9.0 and before does not normalize HTTP URL paths.
  41Plan
• CVE-2019-18802An issue was discovered in Envoy 1.12.0.
  40Plan

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

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.