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CVE-2025-64527

6.5 · MEDIUM

Envoy is a high-performance edge/middle/service proxy.

Published Dec 3, 2025CWE-476EPSS 0.53%

Overview

CVE-2025-64527 is a medium-severity vulnerability. It was published on December 3, 2025 and has a CVSS 3.1 base score of 6.5 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 6.5, rated MEDIUM. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

Technical description

Envoy is a high-performance edge/middle/service proxy. In 1.33.12, 1.34.10, 1.35.6, 1.36.2, and earlier, Envoy crashes when JWT authentication is configured with the remote JWKS fetching, allow_missing_or_failed is enabled, multiple JWT tokens are present in the request headers and the JWKS fetch fails. This is caused by a re-entry bug in the JwksFetcherImpl. When the first token's JWKS fetch fails, onJwksError() callback triggers processing of the second token, which calls fetch() again on the same fetcher object. The original callback's reset() then clears the second fetch's state (receiver_ and request_) which causes a crash when the async HTTP response arrives.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/envoyproxy/envoy/security/advisories/GHSA-mp85-7mrq-r866

How CyberStrike helps

Frequently asked questions

What is CVE-2025-64527?

CVE-2025-64527 is a medium-severity vulnerability. It was published on December 3, 2025 and has a CVSS 3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2025-64527?

This vulnerability has a CVSS 3.1 base score of 6.5, rated MEDIUM. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2025-64527?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2025-64527?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2025-64527 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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