Improper Null Termination Affecting envoyproxy/envoy package, versions [1.8.0, 1.33.13)[1.34.0, 1.34.11)[1.35.0,]
Threat Intelligence
Exploit Maturity
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
Proof of Concept
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- published4 Dec 2025
- disclosed3 Dec 2025
- creditmarkevich.nikita1
Introduced: 3 Dec 2025
NewCVE-2025-66220 (opens in a new tab)Common Vulnerabilities and Exposures (CVE) are common identifiers for publicly known security vulnerabilities
Common Weakness Enumeration (CWE) is a category system for software weaknesses
How to fix?
A fix was pushed into the master branch but not yet published.
Overview
Affected versions of this package are vulnerable to Improper Null Termination in Utility::generalNameAsString. An attacker can bypass certificate validation by presenting a certificate containing an embedded null byte in the OTHERNAME SAN value.
Notes:
- Exploitation of this vulnerability requires Envoy to be set with
require_client_certificateas true and amatch_typed_subject_alt_namesentry for the OTHERNAME OID withmatcher.exact. - The fix for this vulnerability should also be included in v1.35.7 and v1.36.3; however, at the time of updating this advisory, those were not released yet.