CVE-2021-36371: Emissary-Ingress (formerly Ambassador API Gateway) through 1.13.9 allows attackers to bypass client certificat

Q: How do I fix CVE-2021-36371?

emissary-ingress: upgrade to newer than 1.13.9. Exact commands for each OS are on this page.

Q: Is CVE-2021-36371 being exploited?

CVE-2021-36371 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-36371 affect?

CVE-2021-36371 affects emissary-ingress. Severity is low (CVSS 3.7). 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 configura

Q: How urgent is CVE-2021-36371?

Priority 37/100. Public exploit reference; Remotely exploitable, no login, no user action

This week

LOW 3.7REMOTEUPGRADE

CVE-2021-36371 is a low-severity flaw (CVSS 3.7) affecting emissary-ingress. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 una

Why this priority

Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	3.7 (Low)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.7% (top 45%)
CISA exploited list	No
Weakness	CWE-295
Published	2021-07-09
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: getambassador

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-07-09 21:15 UTCPublished CVE record published
2026-06-17 03:58 UTCUpdated Record last modified

getambassador emissary-ingress UPGRADE

Affected: <= 1.13.9

Fixed in: newer than 1.13.9

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy emissary-ingress || rpm -q emissary-ingress || emissary-ingress --version

2. UPGRADE to newer than 1.13.9 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade emissary-ingress

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade emissary-ingress

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-36371?

emissary-ingress: upgrade to newer than 1.13.9. Exact commands for each OS are on this page.

Is CVE-2021-36371 being exploited?

CVE-2021-36371 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-36371 affect?

CVE-2021-36371 affects emissary-ingress. Severity is low (CVSS 3.7). 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 configura

How urgent is CVE-2021-36371?

Priority 37/100. Public exploit reference; Remotely exploitable, no login, no user action

References

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