GHSA-fqg8-vfv7-8fj8 is a critical-severity (CVSS 9.8) CWE-1321 vulnerability in jsonata. O3 Security confirms whether GHSA-fqg8-vfv7-8fj8 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
JSONata expression can pollute the "Object" prototype
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, a proxy for how much of the ecosystem is exposed.
jsonatanpmDescription
Impact
In JSONata versions >= 1.4.0, < 1.8.7 and >= 2.0.0, < 2.0.4, a malicious expression can use the transform operator to override properties on the Object constructor and prototype. This may lead to denial of service, remote code execution or other unexpected behavior in applications that evaluate user-provided JSONata expressions.
Patch
This issue has been fixed in JSONata versions >= 1.8.7 and >= 2.0.4. Applications that evaluate user-provided expressions should update ASAP to prevent exploitation. The following patch can be applied if updating is not possible.
--- a/src/jsonata.js
+++ b/src/jsonata.js
@@ -1293,6 +1293,13 @@ var jsonata = (function() {
}
for(var ii = 0; ii < matches.length; ii++) {
var match = matches[ii];
+ if (match && (match.isPrototypeOf(result) || match instanceof Object.constructor)) {
+ throw {
+ code: "D1010",
+ stack: (new Error()).stack,
+ position: expr.position
+ };
+ }
// evaluate the update value for each match
var update = await evaluate(expr.update, match, environment);
// update must be an object
@@ -1539,7 +1546,7 @@ var jsonata = (function() {
if (typeof err.token == 'undefined' && typeof proc.token !== 'undefined') {
err.token = proc.token;
}
- err.position = proc.position;
+ err.position = proc.position || err.position;
}
throw err;
}
@@ -1972,6 +1979,7 @@ var jsonata = (function() {
"T1007": "Attempted to partially apply a non-function. Did you mean ${{{token}}}?",
"T1008": "Attempted to partially apply a non-function",
"D1009": "Multiple key definitions evaluate to same key: {{value}}",
+ "D1010": "Attempted to access the Javascript object prototype", // Javascript specific
"T1010": "The matcher function argument passed to function {{token}} does not return the correct object structure",
"T2001": "The left side of the {{token}} operator must evaluate to a number",
"T2002": "The right side of the {{token}} operator must evaluate to a number",
References
https://github.com/jsonata-js/jsonata/releases/tag/v2.0.4
Credit
Thank you to Albert Pedersen of Cloudflare for disclosing this issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | jsonata | ≥ 1.4.0&&< 1.8.7 | 1.8.7 |
| 📦npm | jsonata | ≥ 2.0.0&&< 2.0.4 | 2.0.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for jsonata. 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 jsonata to 1.8.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fqg8-vfv7-8fj8 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-fqg8-vfv7-8fj8 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-fqg8-vfv7-8fj8. 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-fqg8-vfv7-8fj8 in your dependencies?
O3 detects GHSA-fqg8-vfv7-8fj8 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.