CVE-2020-15104: In Envoy before versions 1.12.6, 1.13.4, 1.14.4, and 1.15.0 when validating TLS certificates, Envoy would incorrectly allow a wildcard DNS Subject Alt...

Description

In Envoy before versions 1.12.6, 1.13.4, 1.14.4, and 1.15.0 when validating TLS certificates, Envoy would incorrectly allow a wildcard DNS Subject Alternative Name apply to multiple subdomains. For example, with a SAN of *.example.com, Envoy would incorrectly allow nested.subdomain.example.com, when it should only allow subdomain.example.com. This defect applies to both validating a client TLS certificate in mTLS, and validating a server TLS certificate for upstream connections. This vulnerability is only applicable to situations where an untrusted entity can obtain a signed wildcard TLS certificate for a domain of which you only intend to trust a subdomain of. For example, if you intend to trust api.mysubdomain.example.com, and an untrusted actor can obtain a signed TLS certificate for *.example.com or *.com. Configurations are vulnerable if they use verify_subject_alt_name in any Envoy version, or if they use match_subject_alt_names in version 1.14 or later. This issue has been fixed in Envoy versions 1.12.6, 1.13.4, 1.14.4, 1.15.0.

Metrics

CVSS 3.1

5.4/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

EPSS Probability

0.25%

16.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Envoyproxy	Envoy	< 1.12.6
Envoyproxy	Envoy	>= 1.13.0, < 1.13.4
Envoyproxy	Envoy	>= 1.14.0, < 1.14.4

References

https://github.com/envoyproxy/envoy/security/advisories/GHSA-w5f5-6qhq-hhrgThird Party Advisory
https://github.com/envoyproxy/envoy/security/advisories/GHSA-w5f5-6qhq-hhrgThird Party Advisory

Timeline

Published: Jul 14, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-15104?

In Envoy before versions 1.12.6, 1.13.4, 1.14.4, and 1.15.0 when validating TLS certificates, Envoy would incorrectly allow a wildcard DNS Subject Alternative Name apply to multiple subdomains. For example, with a SAN of *.example.com, Envoy would incorrectly allow nested.subdomain.example.com, when it should only allow subdomain.example.com. This defect applies to both validating a client TLS certificate in mTLS, and validating a server TLS certificate for upstream connections. This vulnerability is only applicable to situations where an untrusted entity can obtain a signed wildcard TLS certificate for a domain of which you only intend to trust a subdomain of. For example, if you intend to trust api.mysubdomain.example.com, and an untrusted actor can obtain a signed TLS certificate for *.example.com or *.com. Configurations are vulnerable if they use verify_subject_alt_name in any Envoy version, or if they use match_subject_alt_names in version 1.14 or later. This issue has been fixed in Envoy versions 1.12.6, 1.13.4, 1.14.4, 1.15.0.

How severe is CVE-2020-15104?

CVE-2020-15104 has a CVSS score of 5.4/10 (MEDIUM severity). The EPSS model estimates a 0.25% probability of exploitation in the next 30 days.

How do I fix CVE-2020-15104?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.