CVE-2025-66220 Envoy's TLS certificate matcher for `match_typed_subject_alt_names` may incorrectly treat certificates containing an embedded null byte

What is CVE-2025-66220?

CVE-2025-66220 is a medium-severity vulnerability in Envoyproxy Envoy, published on 3 Dec 2025. An attacker needs administrator access to exploit it, with no action from the victim.

Official description

Envoy is a high-performance edge/middle/service proxy. In 1.33.12, 1.34.10, 1.35.6, 1.36.2, and earlier, Envoy’s mTLS certificate matcher for match_typed_subject_alt_names may incorrectly treat certificates containing an embedded null byte (\0) inside an OTHERNAME SAN value as valid matches.

Weakness: CWE-170

Which versions are affected by CVE-2025-66220?

9 open source packages ship an affected version, including github.com/envoyproxy/envoy and envoy. It affects 1 product.

Products include Envoyproxy Envoy.

How do I fix CVE-2025-66220?

Upgrade github.com/envoyproxy/envoy to a fixed version for your release line: 1.33.13, 1.34.11, 1.35.7 or 1.36.3.

Is CVE-2025-66220 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-66220 exists.

Other vulnerabilities in Envoyproxy Envoy

• CVE-2022-29226 Trivial authentication bypass in Envoy Critical 10.0
• CVE-2019-18801 Memory corruption in n/a Critical 9.8
• CVE-2019-18802 Security feature bypass in n/a Critical 9.8
• CVE-2020-35470 Information disclosure in n/a High 8.8
• CVE-2024-23324 Envoy ext auth can be bypassed when Proxy protocol filter sets invalid UTF-8 metadata High 8.6

All Envoyproxy Envoy vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BIT-envoy-2025-66220, GHSA-rwjg-c3h2-f57p.