CVE-2025-64527: Envoy crashes when JWT authentication is configured with the remote JWKS fetching

CVE-2025-64527 · Severity: medium · CVSS 6.5 · Published 2025-12-03

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.

Technologies: github.com/envoyproxy/envoy (Go). Vendors: Go.

Quick answers

Is CVE-2025-64527 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2025-64527 being exploited in the wild.
How severe is CVE-2025-64527?
Medium severity, with a CVSS score of 6.5, published 3 December 2025.
Which products and versions are affected?
github.com/envoyproxy/envoy (Go) SEMVER:introduced=1.36.0,fixed=1.36.3.
Is there a fix for CVE-2025-64527?
Yes. github.com/envoyproxy/envoy (Go): upgrade to 1.36.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2025-64527?
Check whether you run github.com/envoyproxy/envoy (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • github.com/envoyproxy/envoy (Go): upgrade to 1.36.3 or later
    go get github.com/envoyproxy/envoy@v1.36.3

Affected products

  • github.com/envoyproxy/envoy (Go) SEMVER:introduced=1.36.0,fixed=1.36.3

Identifiers

  • CVE-2025-64527
  • GHSA-mp85-7mrq-r866

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