How severe is CVE-2025-64527?

CVE-2025-64527 has a CVSS score of 6.5/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2025-64527?

CVE-2025-64527 affects the following packages: github.com/envoyproxy/envoy (Go), github.com/envoyproxy/envoy (Go), github.com/envoyproxy/envoy (Go), github.com/envoyproxy/envoy (Go). Ecosystems affected: Go.

How do I fix CVE-2025-64527?

Update github.com/envoyproxy/envoy to 1.36.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-64527 is resolved across your whole dependency graph.

How do I detect CVE-2025-64527 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/envoyproxy/envoy, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2025-64527 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2025-64527 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-64527 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2025-64527?

CVE-2025-64527 has an EPSS (Exploit Prediction Scoring System) score of 0.6%, placing it in the 47th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2025-64527?

CVE-2025-64527 is classified as NULL Pointer Dereference (CWE-476). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2025-64527 published, and has it been updated?

CVE-2025-64527 was published on December 3, 2025 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹

🐹 Go

Not in CISA KEV

MEDIUM severity

CVE-2025-64527 — envoy

MEDIUM

CVE-2025-64527 is a medium-severity (CVSS 6.5) NULL Pointer Dereference vulnerability in github.com/envoyproxy/envoy. A fix is available for github.com/envoyproxy/envoy — see the affected versions and patch details below.

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

Also known asBIT-envoy-2025-64527GHSA-mp85-7mrq-r866

Published

Dec 3, 2025

Updated

Oct 28, 2026

Affected

4 pkgs

Patched

4 / 4

Exploits

None indexed

Exploitation data as of Nov 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-64527.

EPSS Exploitation Probability

via FIRST.org ↗

0.6%probability of exploitation in next 30 days

Lower Risk+0.03%

Lower risk than most CVEs47th percentile — riskier than 47% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

4 pkgs affected

🐹github.com/envoyproxy/envoy🐹github.com/envoyproxy/envoy🐹github.com/envoyproxy/envoy🐹github.com/envoyproxy/envoy

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

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

Affected Packages

4 total 4 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/envoyproxy/envoy`	≥ 1.36.0&&< 1.36.3	1.36.3`go get github.com/envoyproxy/envoy@v1.36.3`
🐹Go	`github.com/envoyproxy/envoy`	≥ 1.35.0&&< 1.35.7	1.35.7`go get github.com/envoyproxy/envoy@v1.35.7`
🐹Go	`github.com/envoyproxy/envoy`	≥ 1.34.0&&< 1.34.11	1.34.11`go get github.com/envoyproxy/envoy@v1.34.11`
🐹Go	`github.com/envoyproxy/envoy`	all versions	1.33.13`go get github.com/envoyproxy/envoy@v1.33.13`

Affected Products

1 product · 4 configurations

Application

envoyenvoyproxy

≥ 1.36.0 && < 1.36.3

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/envoyproxy/envoy, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/envoyproxy/envoy to 1.36.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-64527 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

### 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 arrive

O3 Security · Impact-Aware SCA

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CVSS Score

6.5/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Raw vector

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

CWE Classification

CWE-476NULL Pointer Dereference

Weaponization

No Nuclei template, Metasploit module or public proof-of-concept found.

Timeline

Disclosed

Dec 3, 2025

Last updated

Oct 28, 2026

Identifiers

CVE-2025-64527

GHSA-mp85-7mrq-r866

BIT-envoy-2025-64527

References

Advisorygithub.com · CVE 2025 64527.json Advisorygithub.com · GHSA mp85 7mrq r866 Advisorynvd.nist.gov · CVE 2025 64527 Packagegithub.com · envoy

Related vulnerabilities

This CVE is medium severity; 7 of 8 other CVEs affecting envoy are rated as high or higher (top: high).

CVE-2026-26310CVE-2026-26309CVE-2026-26311CVE-2026-26330CVE-2026-26308CVE-2025-64763CVE-2025-66220CVE-2025-54588

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedOct 28, 2026

CVE-2025-64527 — envoy

Exploitation Status

No confirmed exploitation observed yet

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

Description

Summary

Details

PoC

Impact

Mitigation

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Frequently Asked Questions

Is CVE-2025-64527 in your dependencies?