Improper Null Termination Affecting envoyproxy/envoy package, versions [1.8.0, 1.33.13)[1.34.0, 1.34.11)[1.35.0,1.35.7)[1.36.0,1.36.3)
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-UNMANAGED-ENVOYPROXYENVOY-14176103
- published4 Dec 2025
- disclosed3 Dec 2025
- creditmarkevich.nikita1
Introduced: 3 Dec 2025
CVE-2025-66220 (opens in a new tab)How to fix?
Upgrade envoyproxy/envoy to version 1.33.13, 1.34.11, 1.35.7, 1.36.3 or higher.
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.