Inefficient Regular Expression Complexity in shescapeGHSA-cr84-xvw4-qx3c
HIGHFix: ericcornelissen/shescape@552e8eaGHSA-cr84-xvw4-qx3c is a high-severity (CVSS 7.5) CWE-1333 vulnerability in shescape. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for shescape — see the affected versions and patch details below.
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for GHSA-cr84-xvw4-qx3c.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
shescapenpmDescription
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 | 1.6.1npm install shescape@1.6.1 |
Affected Products
shescapeshescape_projectResearch 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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Frequently Asked Questions
Is GHSA-cr84-xvw4-qx3c in your dependencies?
Find it across npm, including transitive dependencies.