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
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
locutusnpmDescription
Summary
A Prototype Pollution vulnerability exists in the the npm package locutus (>2.0.12). Despite a previous fix that attempted to mitigate Prototype Pollution by checking whether user input contained a forbidden key, it is still possible to pollute Object.prototype via a crafted input using String.prototype. This issue was fixed in version 2.0.39.
Details
The vulnerability resides in line 77 to 79 of https://github.com/locutusjs/locutus/blob/main/src/php/strings/parse_str.js where includes() function is used to check whether user provided input contain forbidden strings.
PoC
Steps to reproduce
- Install latest version of locutus using npm install or cloning from git
- Run the following code snippet:
String.prototype.includes = () => false;
console.log({}.polluted);
const locutus = require('locutus');
locutus.php.strings.parse_str('constructor[prototype][polluted]=yes');
console.log({}.polluted); // prints yes -> indicating that the patch was bypassed and Prototype Pollution occurred
Expected behavior
Prototype Pollution should be prevented and {} should not gain new properties. This should be printed on the console:
undefined
undefined OR throw an Error
Actual behavior
Object.prototype is polluted This is printed on the console:
undefined
yes
Impact
This is a Prototype Pollution vulnerability, which can have severe security implications depending on how locutus is used by downstream applications. Any application that processes attacker-controlled input using this locutus.php.strings.parse_str may be affected. It could potentially lead to the following problems:
- Authentication bypass
- Denial of service
- Remote code execution (if polluted property is passed to sinks like eval or child_process)
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | locutus | ≥ 2.0.12&&< 2.0.39 | 2.0.39 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for locutus. 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 locutus to 2.0.39 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-rxrv-835q-v5mh 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-rxrv-835q-v5mh 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-rxrv-835q-v5mh. 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-rxrv-835q-v5mh in your dependencies?
O3 detects GHSA-rxrv-835q-v5mh across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.