GHSA-g9vw-6pvx-7gmw
HIGHEnvoy: Race condition in Dynamic Forward Proxy leads to use-after-free and segmentation faults
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.
Blast Radius
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 | 1.35.1 |
| 🐹Go | github.com/envoyproxy/envoy | ≥ 1.34.0&&< 1.34.5 | 1.34.5 |
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. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
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 GHSA-g9vw-6pvx-7gmw 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 pinpoints whether GHSA-g9vw-6pvx-7gmw is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-g9vw-6pvx-7gmw. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-g9vw-6pvx-7gmw in your dependencies?
O3 detects GHSA-g9vw-6pvx-7gmw across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.