What’s Vulnerable › Vulnerabilities

CVE-2021-36371

• Severity: low (CVSS 3.7 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-07-09 · updated 2026-06-17
• Weakness: CWE-295

Description

Emissary-Ingress (formerly Ambassador API Gateway) through 1.13.9 allows attackers to bypass client certificate requirements (i.e., mTLS cert_required) on backend upstreams when more than one TLSContext is defined and at least one configuration exists that does not require client certificate authentication. The attacker must send an SNI specifying an unprotected backend and an HTTP Host header specifying a protected backend. (2.x versions are unaffected. 1.x versions are unaffected with certain configuration settings involving prune_unreachable_routes and a wildcard Host resource.)

Affected products

• Getambassador Emissary-Ingress: through 1.13.9

References

• https://github.com/emissary-ingress/emissary/issues/3340
• https://github.com/emissary-ingress/emissary/releases/tag/v2.0.0-ea
• https://github.com/emissary-ingress/emissary/issues/3340
• https://github.com/emissary-ingress/emissary/releases/tag/v2.0.0-ea

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