CVE-2026-123567
Published:November 08, 2026
Updated:November 09, 2026
Sveltejs devalue before 5.6.4 contains a prototype injection vulnerability that allows attackers to inject proto own properties into objects returned by devalue.parse and devalue.unflatten. Attackers can supply crafted serialized input that, when downstream code merges results via Object.assign, alters the target object's prototype.
Affected Packages
https://github.com/sveltejs/devalue.git (GITHUB):
Affected version(s) >=v4.0.0 <v5.6.4 || >=v5.0.0 <v5.6.4Fix Suggestion:
Update to version v5.6.4devalue (NPM):
Affected version(s) >=4.0.0 <5.6.4 || >=5.0.0 <5.6.4Fix Suggestion:
Update to version 5.6.4Additional Notes
The description of this vulnerability differs from MITRE.
Related Resources (7)
Do you need more information?
Contact UsCVSS v4
Base Score:
6.3
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
PRESENT
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
LOW
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
Exploit Maturity
UNREPORTED
CVSS v3
Base Score:
3.7
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
NONE
Weakness Type (CWE)
Improperly Controlled Modification of Object Prototype Attributes
EPSS
Base Score:
0.24