What is CVE-2025-66220?

CVE-2025-66220 is a medium-severity vulnerability in Envoyproxy Envoy, classified under Improper Null Termination. CVSS score: 5.0/10. Published 2025-12-03.

How severe is CVE-2025-66220?

Medium severity. CVSS v3 base score is 5.0 out of 10.

Vulnerability in Envoyproxy Envoy

CVE-2025-66220

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.

EPSS: 0.002 (6.0th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.0 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:L/A:N.

Affected products

Envoyproxy Envoy — versions >= 1.36.0, <= 1.36.2, >= 1.35.0, <= 1.35.6, >= 1.34.0, <= 1.34.10

Weakness classification (CWE)

CWE-170 — Improper Null Termination

References

security-advisories@github.com (x_refsource_CONFIRM, Exploit, Vendor Advisory)

Frequently asked questions

What is CVE-2025-66220?: CVE-2025-66220 is a medium-severity vulnerability in Envoyproxy Envoy, classified under Improper Null Termination. CVSS score: 5.0/10. Published 2025-12-03.
How severe is CVE-2025-66220?: Medium severity. CVSS v3 base score is 5.0 out of 10.