GHSA-hfrv-h3q8-9jpr
MEDIUMkurwov vulnerable to Denial of Service due to improper data sanitization
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
kurwovReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.
Description
Summary
An unsafe sanitization of dataset contents on the MarkovData#getNext method used in Markov#generate and Markov#choose allows a maliciously crafted string on the dataset to throw and stop the function from running properly.
Details
If a string contains a forbidden substring (i.e. __proto__) followed by a space character, the second line will access a special property in MarkovData#finalData by removing the last character of the string, bypassing the dataset sanitization (as it is supposed to be already sanitized before this function is called).
data is then defined as the special function found in its prototype instead of an array.
On the last line, data is then indexed by a random number, which is supposed to return a string but returns undefined as it's a function. Calling endsWith then throws.
PoC
https://runkit.com/embed/m6uu40r5ja9b
Impact
Any dataset can be contaminated with the substring making it unable to properly generate anything in some cases.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | kurwov | ≥ 3.1.0&&< 3.2.5 | 3.2.5 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for kurwov. 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 kurwov to 3.2.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-hfrv-h3q8-9jpr 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-hfrv-h3q8-9jpr 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-hfrv-h3q8-9jpr. 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-hfrv-h3q8-9jpr in your dependencies?
O3 detects GHSA-hfrv-h3q8-9jpr across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.