CVE-2025-54588
Envoy: Race condition in Dynamic Forward Proxy leads to use-after-free and segmentation faults
Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. Versions 1.34.0 through 1.34.4 and 1.35.0 contain a use-after-free (UAF) vulnerability in the DNS cache, causing abnormal process termination. The vulnerability is in Envoy's Dynamic Forward Proxy implementation, occurring when a completion callback for a DNS resolution triggers new DNS resolutions or removes existing pending resolutions. This condition may occur when the following conditions are met: dynamic Forwarding Filter is enabled, the envoy.reloadable_features.dfp_cluster_resolves_hosts runtime flag is enabled, and the Host header is modified between the Dynamic Forwarding Filter and Router filters. This issue is resolved in versions 1.34.5 and 1.35.1. To work around this issue, set the envoy.reloadable_features.dfp_cluster_resolves_hosts runtime flag to false.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
Envoy: Race condition in Dynamic Forward Proxy leads to use-after-free and segmentation faults
Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. Versions 1.34.0 through 1.34.4 and 1.35.0 contain a use-after-free (UAF) vulnerability in the DNS cache, causing abnormal process termination. The vulnerability is in Envoy's Dynamic Forward Proxy implementation, occurring when a completion callback for a DNS resolution triggers new DNS resolutions or removes existing pending resolutions. This condition may occur when the following conditions are met: dynamic Forwarding Filter is enabled, the envoy.reloadable_features.dfp_cluster_resolves_hosts runtime flag is enabled, and the Host header is modified between the Dynamic Forwarding Filter and Router filters. This issue is resolved in versions 1.34.5 and 1.35.1. To work around this issue, set the envoy.reloadable_features.dfp_cluster_resolves_hosts runtime flag to false.
- Record
CVE-2025-54588- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-416
- Updated
- 2026-11-02
EUVDEUVD-2025-26470
Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. Versions 1.34.0 through 1.34.4 and 1.35.0 contain a use-after-free (UAF) vulnerability in the DNS cache, causing abnormal process termination. The vulnerability is in Envoy's Dynamic Forward Proxy implementation, occurring when a completion callback for a DNS resolution triggers new DNS resolutions or removes existing pending resolutions. This condition may occur when the following conditions are met: dynamic Forwarding Filter is enabled, the envoy.reloadable_features.dfp_cluster_resolves_hosts runtime flag is enabled, and the Host header is modified between the Dynamic Forwarding Filter and Router filters. This issue is resolved in versions 1.34.5 and 1.35.1. To work around this issue, set the envoy.reloadable_features.dfp_cluster_resolves_hosts runtime flag to false.
- Record
EUVD-2025-26470- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-g9vw-6pvx-7gmw
Envoy: Race condition in Dynamic Forward Proxy leads to use-after-free and segmentation faults
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:
- Dynamic Forwarding Filter is enabled.
envoy.reloadable_features.dfp_cluster_resolves_hostsruntime flag is enabled.- 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.reloadable_features.dfp_cluster_resolves_hosts runtime flag to false.
Detection
Abnormal process termination with the Envoy::Event::DispatcherImpl::runPostCallbacks() frame in the call stack.
Credits
Rohit Agrawal (agrawroh) ([email protected])
- Record
GHSA-g9vw-6pvx-7gmw- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-416
- Updated
- 2026-11-02
NVD
Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. Versions 1.34.0 through 1.34.4 and 1.35.0 contain a use-after-free (UAF) vulnerability in the DNS cache, causing abnormal process termination. The vulnerability is in Envoy's Dynamic Forward Proxy implementation, occurring when a completion callback for a DNS resolution triggers new DNS resolutions or removes existing pending resolutions. This condition may occur when the following conditions are met: dynamic Forwarding Filter is enabled, the envoy.reloadable_features.dfp_cluster_resolves_hosts runtime flag is enabled, and the Host header is modified between the Dynamic Forwarding Filter and Router filters. This issue is resolved in versions 1.34.5 and 1.35.1. To work around this issue, set the envoy.reloadable_features.dfp_cluster_resolves_hosts runtime flag to false.
- Record
CVE-2025-54588- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-416
- Updated
- 2026-11-02
OSV
Envoy: Race condition in Dynamic Forward Proxy leads to use-after-free and segmentation faults
Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. Versions 1.34.0 through 1.34.4 and 1.35.0 contain a use-after-free (UAF) vulnerability in the DNS cache, causing abnormal process termination. The vulnerability is in Envoy's Dynamic Forward Proxy implementation, occurring when a completion callback for a DNS resolution triggers new DNS resolutions or removes existing pending resolutions. This condition may occur when the following conditions are met: dynamic Forwarding Filter is enabled, the envoy.reloadable_features.dfp_cluster_resolves_hosts runtime flag is enabled, and the Host header is modified between the Dynamic Forwarding Filter and Router filters. This issue is resolved in versions 1.34.5 and 1.35.1. To work around this issue, set the envoy.reloadable_features.dfp_cluster_resolves_hosts runtime flag to false.
- Record
CVE-2025-54588- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-416
- Updated
- 2026-11-02
OSVGHSA-g9vw-6pvx-7gmw
Envoy: Race condition in Dynamic Forward Proxy leads to use-after-free and segmentation faults
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:
- Dynamic Forwarding Filter is enabled.
envoy.reloadable_features.dfp_cluster_resolves_hostsruntime flag is enabled.- 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.reloadable_features.dfp_cluster_resolves_hosts runtime flag to false.
Detection
Abnormal process termination with the Envoy::Event::DispatcherImpl::runPostCallbacks() frame in the call stack.
Credits
Rohit Agrawal (agrawroh) ([email protected])
- Record
GHSA-g9vw-6pvx-7gmw- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-416
- Updated
- 2026-11-02
OSVBIT-envoy-2025-54588 No score
Envoy: Race condition in Dynamic Forward Proxy leads to use-after-free and segmentation faults
Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. Versions 1.34.0 through 1.34.4 and 1.35.0 contain a use-after-free (UAF) vulnerability in the DNS cache, causing abnormal process termination. The vulnerability is in Envoy's Dynamic Forward Proxy implementation, occurring when a completion callback for a DNS resolution triggers new DNS resolutions or removes existing pending resolutions. This condition may occur when the following conditions are met: dynamic Forwarding Filter is enabled, the envoy.reloadable_features.dfp_cluster_resolves_hosts runtime flag is enabled, and the Host header is modified between the Dynamic Forwarding Filter and Router filters. This issue is resolved in versions 1.34.5 and 1.35.1. To work around this issue, set the envoy.reloadable_features.dfp_cluster_resolves_hosts runtime flag to false.
- Record
BIT-envoy-2025-54588- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
github.com/envoyproxy/envoyGo |
1.35.0 to 1.35.0 | 1.35.1 |
github.com/envoyproxy/envoyGo |
1.34.0 up to 1.34.5 | 1.34.5 |
envoyBitnami |
1.34.0 up to 1.34.5, 1.35.0 up to 1.35.1 | 1.34.51.35.1 |
github.com/envoyproxy/envoyGo |
1.35.0 up to 1.35.1 | 1.35.1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2025-54588 is a high vulnerability (CVSS 7.5) in Envoyproxy Envoy, published September 2, 2025. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.50%, the 42nd percentile. Fixed in github.com/envoyproxy/envoy 1.35.1.
References
github.com/envoyproxy/envoy/security/advisories/GHSA-g9vw-6pvx-7gmw
nvd.nist.gov/vuln/detail/CVE-2025-54588