CVE-2021-32777

What it is

Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. In affected versions when ext-authz extension is sending request headers to the external authorization service it must merge multiple value headers according to the HTTP spec. However, only the last header value is sent. This may allow specifically crafted requests to bypass authorization. Attackers may be able to escalate privileges when using ext-authz extension or back end service that uses multiple value headers for authorization. A specifically constructed request may be delivered by an untrusted downstream peer in the presence of ext-authz extension. Envoy versions 1.19.1, 1.18.4, 1.17.4, 1.16.5 contain fixes to the ext-authz extension to correctly merge multiple request header values, when sending request for authorization.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure.

Exploit odds

3.3% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-08-24 21:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:53 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 3.3% in the next 30 days (EPSS).
• Severity: 8.6 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-08-24 21:15 UTC

Last modified

2026-06-17 03:53 UTC

Exploit probability

3.3% · EPSS, next 30 days

Weakness

CWE-551

Record status

Modified

Affected

• Envoyproxy Envoy < 1.16.5
• Envoyproxy Envoy < 1.17.4
• Envoyproxy Envoy < 1.18.4
• Envoyproxy Envoy 1.19.0

Attack profile CVSS 3.1 · 8.6

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Changed

Confidentiality

High

Integrity

None

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-32777.md and follow it. Check whether this project is affected by CVE-2021-32777. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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