CVE-2025-62504

MEDIUM
Published Oct 16, 2025 Modified Oct 29, 2025 CWE-416

Description

Envoy is an open source edge and service proxy. Envoy versions earlier than 1.36.2, 1.35.6, 1.34.10, and 1.33.12 contain a use-after-free vulnerability in the Lua filter. When a Lua script executing in the response phase rewrites a response body so that its size exceeds the configured per_connection_buffer_limit_bytes (default 1MB), Envoy generates a local reply whose headers override the original response headers, leaving dangling references and causing a crash. This results in denial of service. Updating to versions 1.36.2, 1.35.6, 1.34.10, or 1.33.12 fixes the issue. Increasing per_connection_buffer_limit_bytes (and for HTTP/2 the initial_stream_window_size) or increasing per_request_buffer_limit_bytes / request_body_buffer_limit can reduce the likelihood of triggering the condition but does not correct the underlying memory safety flaw.

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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-416 Use After Free

Affected Products

Vendor Product
envoyproxy envoy
envoyproxy envoy
envoyproxy envoy
envoyproxy envoy

References

Frequently Asked Questions

What is CVE-2025-62504? +
Envoy is an open source edge and service proxy. Envoy versions earlier than 1.36.2, 1.35.6, 1.34.10, and 1.33.12 contain a use-after-free vulnerability in the Lua filter. When a Lua script executing in the response phase rewrites a response body so that its size exceeds the configured per_connection_buffer_limit_bytes (default 1MB), Envoy generates a local reply whose headers override the original response headers, leaving dangling references and causing a crash. This results in denial of service. Updating to versions 1.36.2, 1.35.6, 1.34.10, or 1.33.12 fixes the issue. Increasing per_connection_buffer_limit_bytes (and for HTTP/2 the initial_stream_window_size) or increasing per_request_buffer_limit_bytes / request_body_buffer_limit can reduce the likelihood of triggering the condition but does not correct the underlying memory safety flaw. It has a CVSS v3.1 base score of 6.5 (MEDIUM).
How severe is CVE-2025-62504? +
CVE-2025-62504 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-2025-62504? +
CVE-2025-62504 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-2025-62504? +
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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