Envoy: Race condition in Dynamic Forward Proxy leads to use-after-free and segmentation faults

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2025-54588: 0.50% estimated exploitation activity in the next 30 days; percentile 42.50 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary A use-after-free (UAF) vulnerability in Envoy's DNS cache causes abnormal process termination. Envoy may reallocate memory when processing a pending DNS resolution, causing list iterator to reference freed memory. Details The vulnerability exists in Envoy's Dynamic Forward Proxy implementation starting from version v1.34.0. The issue occurs when a completion callback for a DNS resolution triggers new DNS resolutions or removes existing pending resolutions. This condition may occur in the following configuration: 1. Dynamic Forwarding Filter is enabled. 2. envoy.reloadablefeatures.dfpclusterresolveshosts runtime flag is enabled. 3. The Host header is modified between the Dynamic Forwarding Filter and Router filters. Impact Denial of service due to abnormal process termination. Attack vector(s) Request to Envoy configured as indicated above. Patches Users should upgrade to v1.35.1 or v1.34.5. Workaround Set the envoy.reloadablefeatures.dfpclusterresolveshosts runtime flag to…

Published by the source

15 Sep 2025, 16:46 UTC

Last modified by the source

15 Sep 2025, 16:46 UTC

Source last checked

26 Oct 2026, 15:10 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-g9vw-6pvx-7gmw

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# Patch Next advisory brief: CVE-2025-54588

Advisory: Envoy: Race condition in Dynamic Forward Proxy leads to use-after-free and segmentation faults
IDs: CVE-2025-54588, GHSA-g9vw-6pvx-7gmw
Record: https://patchnext.com/advisories/cve-2025-54588 (revision 1, source checked 26 Oct 2026, 15:10 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/envoyproxy/envoy 1.35.1, 1.34.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/envoyproxy/envoy: affected >= 1.35.0, <= 1.35.0; >= 1.34.0, < 1.34.5; fixed in 1.35.1, 1.34.5

## Suggested inspection (read-only)
- Go github.com/envoyproxy/envoy: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/envoyproxy/envoy.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-g9vw-6pvx-7gmw (GitHub-reviewed advisory GHSA-g9vw-6pvx-7gmw lists affected ranges: Go github.com/envoyproxy/envoy >=1.35.0 =1.34.0 <1.34.5)

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