GHSA-3329-pjwv-fjpg
MEDIUMGHSA-3329-pjwv-fjpg is a medium-severity (CVSS 6.5) Improper Input Validation vulnerability in urijs. O3 Security confirms whether GHSA-3329-pjwv-fjpg is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Hostname spoofing via backslashes in URL
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
urijsnpmDescription
Impact
If using affected versions to determine a URL's hostname, the hostname can be spoofed by using a backslash (\) character followed by an at (@) character. If the hostname is used in security decisions, the decision may be incorrect.
Depending on library usage and attacker intent, impacts may include allow/block list bypasses, SSRF attacks, open redirects, or other undesired behavior.
Example URL: https://expected-example.com\@observed-example.com
Escaped string: https://expected-example.com\\@observed-example.com (JavaScript strings must escape backslash)
Affected versions incorrectly return observed-example.com. Patched versions correctly return expected-example.com. Patched versions match the behavior of other parsers which implement the WHATWG URL specification, including web browsers and Node's built-in URL class.
Patches
Version 1.19.4 is patched against all known payload variants. Version 1.19.3 has a partial patch but is still vulnerable to a payload variant.
References
https://github.com/medialize/URI.js/releases/tag/v1.19.4 (complete fix for this bypass) https://github.com/medialize/URI.js/releases/tag/v1.19.3 (partial fix for this bypass) PR #233 (initial fix for backslash handling)
For more information
If you have any questions or comments about this advisory, open an issue in https://github.com/medialize/URI.js
Reporter credit
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | urijs | all versions | 1.19.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for urijs. 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 urijs to 1.19.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-3329-pjwv-fjpg 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-3329-pjwv-fjpg 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-3329-pjwv-fjpg. 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-3329-pjwv-fjpg in your dependencies?
O3 detects GHSA-3329-pjwv-fjpg across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.