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Envoy crashes when JWT authentication is configured with the remote JWKS fetching

Moderate severity GitHub Reviewed Published Dec 3, 2025 in envoyproxy/envoy

Package

gomod github.com/envoyproxy/envoy (Go)

Affected versions

>= 1.36.0, <= 1.36.2
>= 1.35.0, <= 1.35.6
>= 1.34.0, <= 1.34.10
<= 1.33.12

Patched versions

1.36.3
1.35.7
1.34.11
1.33.13

Description

Summary

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.

Details

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.

PoC

  • allow_missing_or_failed or allow_missing is enabled
  • The client send 2 Authorization headers
  • the remote JWKS fetching failed
  • There will be crash

Impact

DoS and Crash

Mitigation

  • Disable the allow_missing_or_failed or allow_missing

References

@phlax phlax published to envoyproxy/envoy Dec 3, 2025
Published by the National Vulnerability Database Dec 3, 2025
Published to the GitHub Advisory Database Dec 5, 2025
Reviewed Dec 5, 2025

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(33rd percentile)

Weaknesses

NULL Pointer Dereference

A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. Learn more on MITRE.

CVE ID

CVE-2025-64527

GHSA ID

GHSA-mp85-7mrq-r866

Source code

Credits

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