CVE-2026-47778

Summary

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.

Affected Software

VendorProductVersion RangeStatus
envoyproxyenvoy>= 1.38.0, < 1.38.1affected
envoyproxyenvoy>= 1.37.0, < 1.37.3affected
envoyproxyenvoy>= 1.36.0, < 1.36.7affected
envoyproxyenvoy< 1.35.11affected

Weaknesses

  • CWE-158: CWE-158: Improper Neutralization of Null Byte or NUL Character

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: poc
    • Automatable: no
    • Technical Impact: partial

Additional References

References