CVE-2026-47778

Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.35.11, 1.36.7, 1.37.3, and 1.38.1, a structural flaw was identified in DefaultCertValidator::verifySubjectAltName where the extracted DNS SAN string is cast to a C-style string using .c_str() before being passed to the Utility::dnsNameMatch() algorithm. If the attacker serves a certificate with a dNSName SAN containing an embedded NUL byte, the helper Utility::generalNameAsString captures the complete string including the NUL. However, when .c_str() evaluates it, implicit conversion to absl::string_view inside dnsNameMatch relies on strlen(), prematurely truncating the evaluation context. Envoy evaluates trucated string against the exact required config_san match and returns true, thereby successfully validating the string with the Nul byte for an upstream routing. This vulnerability is fixed in 1.35.11, 1.36.7, 1.37.3, and 1.38.1.

• CWE-158

• https://github.com/envoyproxy/envoy/security/advisories/GHSA-f8x4-rw5x-f3r7Exploit, Vendor Advisory, Mitigation
• https://github.com/envoyproxy/envoy/security/advisories/GHSA-f8x4-rw5x-f3r7Exploit, Vendor Advisory, Mitigation

Published

Jun 26, 2026

Last Modified

Jun 29, 2026

Status

Analyzed

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