CVE-2019-9900: Envoyproxy Envoy

High severity, CVSS 8.3. EPSS: 3.7% chance of exploitation in the next 30 days.

When parsing HTTP/1.x header values, Envoy 1.9.0 and before does not reject embedded zero characters (NUL, ASCII 0x0). This allows remote attackers crafting header values containing embedded NUL characters to potentially bypass header matching rules, gaining access to unauthorized resources.

Affected products

• Envoyproxy Envoy: up to and including 1.9.0
• Red Hat Openshift Service Mesh: affected versions not specified

Published 2019-04-25. Last modified 2026-06-17.