CVE-2025-54588 — envoy
HIGHCVE-2025-54588 is a high-severity (CVSS 7.5) Use After Free vulnerability in github.com/envoyproxy/envoy. A fix is available for github.com/envoyproxy/envoy — see the affected versions and patch details below.
Envoy: Race condition in Dynamic Forward Proxy leads to use-after-free and segmentation faults
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- 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-2025-54588.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2025-54588 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/envoyproxy/envoy🐹github.com/envoyproxy/envoyReal-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
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])
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/envoyproxy/envoy | ≥ 1.35.0&&< 1.35.1 | 1.35.1go get github.com/envoyproxy/envoy@v1.35.1 |
| 🐹Go | github.com/envoyproxy/envoy | ≥ 1.34.0&&< 1.34.5 | 1.34.5go get github.com/envoyproxy/envoy@v1.34.5 |
Detection & mitigation playbook
Open-source dependencyDetect
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 1.35.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-54588 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2025-54588 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2025-54588. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat OpenShift Service Mesh 3.0 | openshift-service-mesh/istio-proxyv2-rhel9:1.24.6-1757566151 | RHSA-2025:16040 |
| Red Hat OpenShift Service Mesh 3.1 | openshift-service-mesh/istio-proxyv2-rhel9:1.26.4-1757524855 | RHSA-2025:16044 |
Frequently Asked Questions
Is CVE-2025-54588 in your dependencies?
O3 Security finds CVE-2025-54588 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.