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CVE-2024-27307

JSONata expression can pollute the "Object" prototype

9.8 CriticalFix available

JSONata is a JSON query and transformation language. Starting in version 1.4.0 and prior to version 1.8.7 and 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. 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. As a workaround, one may apply the patch manually.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

1.42%Up 1.4 points since Mar 7, 2024
90%50%10%1%

What each source reports

CVE List Score used 9.8

JSONata expression can pollute the "Object" prototype

JSONata is a JSON query and transformation language. Starting in version 1.4.0 and prior to version 1.8.7 and 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. 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. As a workaround, one may apply the patch manually.

Record
CVE-2024-27307
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-1321
Updated
2026-11-02
EUVDEUVD-2024-0922 9.8

JSONata is a JSON query and transformation language. Starting in version 1.4.0 and prior to version 1.8.7 and 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. 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. As a workaround, one may apply the patch manually.

Record
EUVD-2024-0922
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-03
GitHub AdvisoriesGHSA-fqg8-vfv7-8fj8 9.8

JSONata expression can pollute the "Object" prototype

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.

Record
GHSA-fqg8-vfv7-8fj8
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-1321
Updated
2026-11-02
NVD 9.8

JSONata is a JSON query and transformation language. Starting in version 1.4.0 and prior to version 1.8.7 and 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. 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. As a workaround, one may apply the patch manually.

Record
CVE-2024-27307
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-1321
Updated
2026-11-02
OSV 9.8

JSONata expression can pollute the "Object" prototype

JSONata is a JSON query and transformation language. Starting in version 1.4.0 and prior to version 1.8.7 and 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. 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. As a workaround, one may apply the patch manually.

Record
CVE-2024-27307
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-1321
Updated
2026-11-02
OSVGHSA-fqg8-vfv7-8fj8 9.8

JSONata expression can pollute the "Object" prototype

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.

Record
GHSA-fqg8-vfv7-8fj8
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-1321
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
jsonata
npm
1.4.0 up to 1.8.7
1.8.7
jsonata
npm
2.0.0 up to 2.0.4
2.0.4

History

History
RecordedChangedSources
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2024-27307 is a critical vulnerability (CVSS 9.8) in Jsonata, published March 4, 2024. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.42%, the 73rd percentile. Fixed in jsonata 1.8.7.

References

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