What’s Vulnerable › Vulnerabilities

CVE-2019-15226

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 64.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2019-10-09 · updated 2026-06-17
• Weakness: CWE-400

Description

Upon receiving each incoming request header data, Envoy will iterate over existing request headers to verify that the total size of the headers stays below a maximum limit. The implementation in versions 1.10.0 through 1.11.1 for HTTP/1.x traffic and all versions of Envoy for HTTP/2 traffic had O(n^2) performance characteristics. A remote attacker may craft a request that stays below the maximum request header size but consists of many thousands of small headers to consume CPU and result in a denial-of-service attack.

Affected products

• envoyproxy envoy: 1.0.0, 1.1.0, 1.2.0, 1.3.0, 1.4.0, 1.5.0 (+10)

References

• https://github.com/envoyproxy/envoy/commit/afc39bea36fd436e54262f150c009e8d72db5014
• https://github.com/envoyproxy/envoy/commits/master
• https://github.com/envoyproxy/envoy/issues/8520
• https://github.com/envoyproxy/envoy/commit/afc39bea36fd436e54262f150c009e8d72db5014
• https://github.com/envoyproxy/envoy/commits/master
• https://github.com/envoyproxy/envoy/issues/8520

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