CVE-2019-9900

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.

• CWE-74

• https://access.redhat.com/errata/RHSA-2019:0741Third Party Advisory
• https://github.com/envoyproxy/envoy/issues/6434Exploit, Issue Tracking, Third Party Advisory
• https://github.com/envoyproxy/envoy/security/advisories/GHSA-x74r-f4mw-c32hExploit, Mitigation, Third Party Advisory
• https://groups.google.com/forum/#%21topic/envoy-announce/VoHfnDqZiAM
• https://www.envoyproxy.io/docs/envoy/v1.9.1/intro/version_historyRelease Notes, Vendor Advisory
• https://access.redhat.com/errata/RHSA-2019:0741Third Party Advisory
• https://github.com/envoyproxy/envoy/issues/6434Exploit, Issue Tracking, Third Party Advisory
• https://github.com/envoyproxy/envoy/security/advisories/GHSA-x74r-f4mw-c32hExploit, Mitigation, Third Party Advisory
• https://groups.google.com/forum/#%21topic/envoy-announce/VoHfnDqZiAM
• https://www.envoyproxy.io/docs/envoy/v1.9.1/intro/version_historyRelease Notes, Vendor Advisory

Published

Apr 25, 2019

Last Modified

Jun 17, 2026

Status

Modified

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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