CVE-2026-47778

Envoy: Embedded NUL in TLS DNS SAN Truncation in the Default TLS Certificate Validator. (Auth Bypass)

MEDIUM

4.4

CVSS Score

Published: June 26, 2026 at 05:27 PM UTC

Updated: October 25, 2026 at 05:10 PM UTC

1 product affected across 1 vendorEnvoy

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Severity

MEDIUM4.4

Exploit prediction

EPSS 0.2%

SSVC

PoC

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Envoy · Envoyproxy

95%

v < 1.35.131.36.0 ≤ v < 1.36.91.37.0 ≤ v < 1.37.51.38.0 ≤ v < 1.38.3

Affected range stops below 1.35.11, so it looks safe — our inference, not a vendor statement

Affected range stops below 1.35.13, so it looks safe — our inference, not a vendor statement

Affected range stops below 1.36.7, so it looks safe — our inference, not a vendor statement

Affected range stops below 1.36.9, so it looks safe — our inference, not a vendor statement

Affected range stops below 1.37.3, so it looks safe — our inference, not a vendor statement

Affected range stops below 1.37.5, so it looks safe — our inference, not a vendor statement

Affected range stops below 1.38.1, so it looks safe — our inference, not a vendor statement

Affected range stops below 1.38.3, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

https://github.com/envoyproxy/envoy/security/advisories/GHSA-f8x4-rw5x-f3r7

References (1)

x_refsource_CONFIRMExploitVendor AdvisoryMitigation

Source: cverecord

https://github.com/envoyproxy/envoy/security/advisories/GHSA-f8x4-rw5x-f3r7

SSVC — Action Prioritization

SSVCPoCNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

4.4MEDIUMGitHub_M

Attack Vector: NETWORK
Complexity: HIGH
Privileges: HIGH
User Interaction: NONE
Scope: UNCHANGED
Confidentiality: HIGH
Integrity: NONE
Availability: NONE

Vector?

Quick Info

StatusANALYZED

CWE

CWE-158

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