CVE-2026-26310

Calling Utility::getAddressWithPort with a scoped IPv6 addresses causes a crash. This utility is called in the data plane from the original_src filter and the dns filter.

Details

The crashing function is Utility::getAddressWithPort. The crash occurs if a string containing a scoped IPv6 address is passed to this function.

This vulnerability affects:

1. The original src filter: If the filter is configured and the original source is a scoped IPv6 address, it will cause a crash.
2. DNS response address resolution: If a DNS response contains a scoped IPv6 address, this will also trigger the crash.

PoC

To reproduce the vulnerability:

1. Method A (Original Src Filter): Configure the original src filter in Envoy and provide a scoped IPv6 address as the original source.
2. Method B (DNS Resolution): Trigger a DNS resolution process within Envoy where the DNS response contains a scoped IPv6 address.

This is a Denial of Service (DoS) vulnerability. It impacts users who have the original src filter configured or whose Envoy instances resolve addresses from DNS responses that may contain scoped IPv6 addresses.

The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.

CVE-2026-26310 has a CVSS score of 5.9 (Medium). 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. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.

Kodem intelligence

1. What is CVE-2026-26310? CVE-2026-26310 is a medium-severity improper input validation vulnerability in github.com/envoyproxy/envoy (go), affecting versions = 1.37.0. No fixed version is listed yet. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
2. How severe is CVE-2026-26310? CVE-2026-26310 has a CVSS score of 5.9 (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.
3. Which versions of github.com/envoyproxy/envoy are affected by CVE-2026-26310? github.com/envoyproxy/envoy (go) versions = 1.37.0 is affected.
4. Is there a fix for CVE-2026-26310? No fixed version is listed for CVE-2026-26310 yet. Monitor the advisory for updates and apply mitigations in the interim.
5. Is CVE-2026-26310 exploitable, and should I be worried? Whether CVE-2026-26310 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-2026-26310 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-2026-26310? No fixed version is listed yet. In the interim: Validate all external input against an allowlist of expected values, types, and ranges before processing.