Is CVE-2021-32777 actively exploited?

No active exploitation of CVE-2021-32777 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2021-32777 be exploited remotely?

Yes. CVE-2021-32777 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2021-32777?

CVE-2021-32777 has a CVSS score of 8.3 (HIGH).

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HIGH

CVE-2021-32777

CWE-551Published: August 24, 2021· Updated: Jun 17, 2026

8.3

CVSS v3.1

Official Description

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.

NVD Source

Technical Analysis

CVE-2021-32777 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

The vulnerability has a "Changed" scope, meaning successful exploitation can impact components beyond the vulnerable component itself — such as the host operating system or adjacent services.