Summary
At the rate limit filter, if we enabled the response phase limit with apply_on_stream_done in the rate limit configuration and the response phase limit request fails directly, it may crash Envoy.
Details
When both the request phase limit and response phase limit are enabled, the safe gRPC client instance will be re-used for both the request phase request and response phase request.
But after the request phase request is done, the inner state of the request phase limit request in gRPC client is not cleaned up. When we send the second limit request at response phase, and the second limit request fails directly, we may access the previous request's inner state and result in crash.
PoC
This need to mock the network failure. But we have reproduced by unit test locally.
To workaround
This could be worked around by splitting the rate limit filter. That is, if there is a rate limit filter that contains normal rate limit configuration (request phase limit, without apply_on_stream_done) and also rate limit configuration with apply_on_stream_done (response phase limit). Splitting them into two rate limit filters and ensure one filter only contains normal rate limit configuration (without apply_on_stream_done), and one only contains rate limit configuration with apply_on_stream_done could avoid this problem.
Credit
Mandar Jog ([email protected])
Impact
This only happens when both the request phase limit and response phase limit are enabled in the rate limit filter, and requires the request to rate limit service fails directly (For example, if from Envoy's perspective, no healthy endpoint for rate limit service may result the request fails directly). That's say, not easy to trigger this.
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-2026-26330 has a CVSS score of 5.3 (Medium). The vector is network-reachable, low 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. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
In the interim: Keep the dependency up to date. In native-code projects, use memory-safe data structures and address sanitizers during testing.
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-26330? CVE-2026-26330 is a medium-severity use after free vulnerability in github.com/envoyproxy/envoy (go), affecting versions = 1.37.0. No fixed version is listed yet. Memory is accessed after it has been freed, leading to undefined behavior in native code.
- How severe is CVE-2026-26330? CVE-2026-26330 has a CVSS score of 5.3 (Medium). 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.
- Which versions of github.com/envoyproxy/envoy are affected by CVE-2026-26330? github.com/envoyproxy/envoy (go) versions = 1.37.0 is affected.
- Is there a fix for CVE-2026-26330? No fixed version is listed for CVE-2026-26330 yet. Monitor the advisory for updates and apply mitigations in the interim.
- Is CVE-2026-26330 exploitable, and should I be worried? Whether CVE-2026-26330 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
- What actually determines whether CVE-2026-26330 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.
- How do I fix CVE-2026-26330? No fixed version is listed yet. In the interim: Keep the dependency up to date. In native-code projects, use memory-safe data structures and address sanitizers during testing.