How severe is GHSA-rwjg-c3h2-f57p?

GHSA-rwjg-c3h2-f57p has a CVSS score of 5/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by GHSA-rwjg-c3h2-f57p?

GHSA-rwjg-c3h2-f57p affects the following packages: github.com/envoyproxy/envoy (Go), github.com/envoyproxy/envoy (Go), github.com/envoyproxy/envoy (Go), github.com/envoyproxy/envoy (Go). Ecosystems affected: Go.

How do I fix GHSA-rwjg-c3h2-f57p?

Update github.com/envoyproxy/envoy to 1.36.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-rwjg-c3h2-f57p is resolved across your whole dependency graph.

How do I detect GHSA-rwjg-c3h2-f57p in my Go dependencies?

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.

How do I mitigate GHSA-rwjg-c3h2-f57p if there is no patch (or I can't update yet)?

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 does O3 Security protect against GHSA-rwjg-c3h2-f57p?

O3 pinpoints whether GHSA-rwjg-c3h2-f57p is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-rwjg-c3h2-f57p actively exploited in the wild?

No public exploit code has been indexed for GHSA-rwjg-c3h2-f57p yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-rwjg-c3h2-f57p?

GHSA-rwjg-c3h2-f57p has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 7th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-rwjg-c3h2-f57p?

GHSA-rwjg-c3h2-f57p is classified as CWE-170 (CWE-170). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-rwjg-c3h2-f57p published, and has it been updated?

GHSA-rwjg-c3h2-f57p was published on December 5, 2025 and was last updated on December 6, 2025. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

GHSA-rwjg-c3h2-f57p

MEDIUM

GHSA-rwjg-c3h2-f57p is a medium-severity (CVSS 5) CWE-170 vulnerability in github.com/envoyproxy/envoy. O3 Security confirms whether GHSA-rwjg-c3h2-f57p is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

Envoy's TLS certificate matcher for `match_typed_subject_alt_names` may incorrectly treat certificates containing an embedded null byte

Also known asBIT-envoy-2025-66220CVE-2025-66220

Published

Dec 5, 2025

Updated

Dec 6, 2025

Affected

4 pkgs

Patched

4 / 4

Exploits

None indexed

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs7th percentile — riskier than 7% of all scored CVEsHighest risk

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.

Real-World Exposure

4 pkgs affected

🐹github.com/envoyproxy/envoy🐹github.com/envoyproxy/envoy🐹github.com/envoyproxy/envoy🐹github.com/envoyproxy/envoy

Real-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

Envoy’s mTLS certificate matcher for match_typed_subject_alt_names may incorrectly treat certificates containing an embedded null byte (\0) inside an OTHERNAME SAN value as valid matches.

Details

This occurs when the SAN is encoded as a BMPSTRING or UNIVERSALSTRING, and its UTF-8 conversion result is truncated at the first null byte during string assignment. As a result, "victim\0evil" may match an exact: "victim" rule and be accepted by Envoy.

PoC

Create a CA and a server certificate signed by that CA. Create two client certificates signed by the same CA: client_evil with OTHERNAME BMPSTRING = "evil" client_null with OTHERNAME BMPSTRING = "victim\0evil" Configure Envoy with require_client_certificate: true and a match_typed_subject_alt_names entry for the OTHERNAME OID with matcher.exact: "victim". Connect without a client cert → connection rejected. Connect with client_evil → connection rejected. Connect with client_null → connection accepted (but shouldn't!).

Impact

An attacker who can obtain a trusted client certificate with a null byte embedded in an OTHERNAME SAN can exploit this vulnerability. The practical impact is unauthorized impersonation of the matched identity, enabling access to services or APIs protected by that exact OTHERNAME check.

Credit

[email protected]

Affected Packages

4 total 4 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/envoyproxy/envoy`	≥ 1.36.0&&< 1.36.3	1.36.3
🐹Go	`github.com/envoyproxy/envoy`	≥ 1.35.0&&< 1.35.7	1.35.7
🐹Go	`github.com/envoyproxy/envoy`	≥ 1.34.0&&< 1.34.11	1.34.11
🐹Go	`github.com/envoyproxy/envoy`	all versions	1.33.13

Detection & mitigation playbook

Open-source dependency

Detect
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 1.36.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-rwjg-c3h2-f57p 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-rwjg-c3h2-f57p 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-rwjg-c3h2-f57p. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Summary Envoy’s mTLS certificate matcher for `match_typed_subject_alt_names` may incorrectly treat certificates containing an embedded null byte (\0) inside an `OTHERNAME` SAN value as valid matches. ### Details This occurs when the SAN is encoded as a `BMPSTRING` or `UNIVERSALSTRING`, and its UTF-8 conversion result is truncated at the first null byte during string assignment. As a result, `"victim\0evil"` may match an exact: `"victim"` rule and be accepted by Envoy. ### PoC Create a CA and a server certificate signed by that CA. Create two client certificates signed by the same CA: cl

O3 Security · Impact-Aware SCA

Is GHSA-rwjg-c3h2-f57p in your dependencies?

O3 detects GHSA-rwjg-c3h2-f57p across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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