CVE-2025-54588

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.reloadable_features.dfp_cluster_resolves_hosts runtime flag is enabled.
3. The Host header is modified between the Dynamic Forwarding Filter and Router filters.

Attack vector(s)

Request to Envoy configured as indicated above.

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])

Denial of service due to abnormal process termination.

Memory is accessed after it has been freed, leading to undefined behavior in native code. Typical impact: memory corruption, crash, or potential code execution.

CVE-2025-54588 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.35.1, 1.34.5); upgrading removes the vulnerable code path.

Kodem intelligence

Users should upgrade to v1.35.1 or v1.34.5.

1. What is CVE-2025-54588? CVE-2025-54588 is a high-severity use after free vulnerability in github.com/envoyproxy/envoy (go), affecting versions = 1.35.0. It is fixed in 1.35.1, 1.34.5. Memory is accessed after it has been freed, leading to undefined behavior in native code.
2. How severe is CVE-2025-54588? CVE-2025-54588 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/envoyproxy/envoy are affected by CVE-2025-54588? github.com/envoyproxy/envoy (go) versions = 1.35.0 is affected.
4. Is there a fix for CVE-2025-54588? Yes. CVE-2025-54588 is fixed in 1.35.1, 1.34.5. Upgrade to this version or later.
5. Is CVE-2025-54588 exploitable, and should I be worried? Whether CVE-2025-54588 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2025-54588 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2025-54588?
   • Upgrade github.com/envoyproxy/envoy to 1.35.1 or later
   • Upgrade github.com/envoyproxy/envoy to 1.34.5 or later