# CVE-2026-47778

## Summary

- **CVE ID:** CVE-2026-47778
- **Severity:** MEDIUM
- **CVSS Score:** 4.4 (CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N)
- **CWE:** CWE-158
- **Published:** Jun 26, 2026
- **Last Modified:** Jun 27, 2026

## Description

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 Products

- envoyproxy — envoy (>= 1.38.0, < 1.38.1)
- envoyproxy — envoy (>= 1.37.0, < 1.37.3)
- envoyproxy — envoy (>= 1.36.0, < 1.36.7)
- envoyproxy — envoy (< 1.35.11)

## References

- [CNA](https://github.com/envoyproxy/envoy/security/advisories/GHSA-f8x4-rw5x-f3r7)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.21%
- **EPSS Percentile:** 11.5

---
_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._