GHSA-cr84-xvw4-qx3c
HIGHInefficient Regular Expression Complexity in shescape
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
shescapeReal-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
Impact
This impacts users that use shescape to escape arguments:
- for the Unix shell Bash, or any not-officially-supported Unix shell;
- using the
escapeorescapeAllfunctions with theinterpolationoption set totrue.
An attacker can cause polynomial backtracking in terms of the input string length due to a Regular Expression in shescape that is vulnerable to Regular Expression Denial of Service (ReDoS). Example:
import * as shescape from "shescape";
/* 1. Prerequisites */
const options = {
interpolation: true,
// and
shell: "/bin/bash",
// or
shell: "some-not-officially-supported-shell",
// or
shell: undefined, // Only if the system's default shell is bash or an unsupported shell.
};
/* 2. Attack */
let userInput = '{,'.repeat(150_000); // polynomial backtracking
/* 3. Usage */
shescape.escape(userInput, options);
// or
shescape.escapeAll([userInput], options);
Patches
This bug has been patched in v1.6.1 which you can upgrade to now. No further changes required.
Workarounds
Alternatively, a maximum length can be enforced on input strings to shescape to reduce the impact of the vulnerability. It is not recommended to try and detect vulnerable input strings, as the logic for this may end up being vulnerable to ReDoS itself.
References
For more information
- Comment on commit 552e8ea
- Open an issue at https://github.com/ericcornelissen/shescape/issues (New issue > Question > Get started)
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | shescape | ≥ 1.5.10&&< 1.6.1 | 1.6.1 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for shescape. 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 shescape to 1.6.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-cr84-xvw4-qx3c 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-cr84-xvw4-qx3c 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-cr84-xvw4-qx3c. 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-cr84-xvw4-qx3c in your dependencies?
O3 detects GHSA-cr84-xvw4-qx3c across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.