GHSA-h289-x5wc-xcv8
MEDIUMImproper Validation of Certificate with Host Mismatch in mellium.im/xmpp/websocket
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
mellium.im/xmppReal-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
Impact
If no TLS configuration is provided by the user, the websocket package constructs its own TLS configuration using recommended defaults. When looking up a WSS endpoint using the DNS TXT record method described in XEP-0156: Discovering Alternative XMPP Connection Methods the ServerName field was incorrectly being set to the name of the server returned by the TXT record request, not the name of the initial server we were attempting to connect to. This means that any attacker that can spoof a DNS record (ie. in the absence of DNSSEC, DNS-over-TLS, DNS-over-HTTPS, or similar technologies) could redirect the user to a server of their choosing and as long as it had a valid TLS certificate for itself the connection would succeed, resulting in a MITM situation.
Patches
All users should upgrade to v0.21.1.
Workarounds
To work around the issue, manually specify a TLS configuration with the correct hostname.
References
For more information
If you have any questions or comments about this advisory:
- Reach out on XMPP to [email protected]
- Email us at [email protected]
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | mellium.im/xmpp | ≥ 0.18.0&&< 0.21.1 | 0.21.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mellium.im/xmpp. 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 mellium.im/xmpp to 0.21.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-h289-x5wc-xcv8 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-h289-x5wc-xcv8 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-h289-x5wc-xcv8. 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-h289-x5wc-xcv8 in your dependencies?
O3 detects GHSA-h289-x5wc-xcv8 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.