CVE-2025-64527

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.

CVSS v3.1 Score

6.5

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness Type (CWE)

CWE-476 CWE-476

Affected Products

Vendor	Product	Versions
envoyproxy	envoy	< 1.33.13
envoyproxy	envoy	1.34.0 — 1.34.11
envoyproxy	envoy	1.35.0 — 1.35.7
envoyproxy	envoy	1.36.0 — 1.36.3

References

Advisories & Patches

https://github.com/envoyproxy/envoy/security/advisories/GHSA-mp85-7mrq-r866

Exploits

https://github.com/envoyproxy/envoy/security/advisories/GHSA-mp85-7mrq-r866

Frequently Asked Questions

What is CVE-2025-64527? +

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. It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2025-64527? +

CVE-2025-64527 has a CVSS v3.1 score of 6.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-64527? +

CVE-2025-64527 affects products from envoyproxy, specifically: envoy. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-64527? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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