CVE-2020-15104
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedIn 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceEnvoy incorrectly validates wildcard DNS Subject Alternative Names in TLS certificates, allowing *.example.com to match nested.subdomain.example.com when it should only match one level (subdomain.example.com). This affects both mTLS client certificate validation and upstream server certificate validation when using verify_subject_alt_name or match_subject_alt_names.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 1.12.6>= 1.13.0, < 1.13.4>= 1.14.0, < 1.14.4CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
-
Determine Envoy versionRun 'envoy --version' or check the binary metadata to identify the installed Envoy versionAffected if The version falls into any of these ranges: < 1.12.6, >= 1.13.0 but < 1.13.4, or >= 1.14.0 but < 1.14.4
-
Locate TLS listener configurationsSearch Envoy configuration files (static or dynamic) for listener definitions that include TLS certificate validation settingsAffected if Listeners use TLS with mTLS client certificate validation
-
Identify subject_alt_name verification settingsSearch for 'verify_subject_alt_name' or 'match_subject_alt_names' fields in TLS configurations for listeners (downstream) or clusters (upstream)Affected if Either verify_subject_alt_name or match_subject_alt_names is configured with wildcard DNS patterns such as '*.example.com'
-
Examine wildcard SAN usage in certificate validationReview the specific DNS patterns listed in verify_subject_alt_name or match_subject_alt_names arrays to identify wildcard usageAffected if Wildcard patterns like '*.example.com' are used for certificate validation in an untrusted multi-level subdomain context
You are affected if your Envoy version is in the vulnerable range AND you have verify_subject_alt_name or match_subject_alt_names configured with wildcard DNS patterns for TLS certificate validation.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor data1.12.61.13.41.14.4
Upgrade Envoy to version 1.12.6, 1.13.4, 1.14.4, or 1.15.0 or later. Review TLS certificate configurations to ensure wildcard SANs are not being used in untrusted multi-level subdomain scenarios.
- Consultation4.0 h
- Implementation8.0 h
- Testing8.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,656.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-15104 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2020-15104 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data