CVE-2026-26310 — envoy
MEDIUMCVE-2026-26310 is a medium-severity (CVSS 5.9) Improper Input Validation vulnerability in github.com/envoyproxy/envoy. No vendor fix is recorded yet; mitigation options are listed below.
Crash for scoped ip address in Envoy during DNS
Exploitation Status
No confirmed exploitation observed yet
- 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-2026-26310.
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-2026-26310 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 378,567 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/envoy🐹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
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:
- The original src filter: If the filter is configured and the original source is a scoped IPv6 address, it will cause a crash.
- DNS response address resolution: If a DNS response contains a scoped IPv6 address, this will also trigger the crash.
PoC
To reproduce the vulnerability:
- Method A (Original Src Filter): Configure the
original srcfilter in Envoy and provide a scoped IPv6 address as the original source. - Method B (DNS Resolution): Trigger a DNS resolution process within Envoy where the DNS response contains a scoped IPv6 address.
Impact
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/envoyproxy/envoy | all versions | No fix |
| 🐹Go | github.com/envoyproxy/envoy | ≥ 1.36.0 | No fix |
| 🐹Go | github.com/envoyproxy/envoy | ≥ 1.35.0 | No fix |
| 🐹Go | github.com/envoyproxy/envoy | all versions | No fix |
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.
Remediation status
No patched version of github.com/envoyproxy/envoy has shipped for CVE-2026-26310 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
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-2026-26310 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-26310. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-26310 in your dependencies?
O3 Security finds CVE-2026-26310 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.