Prototype Pollution in Sveltejs Devalue
CVE-2026-123568
Sveltejs devalue before 5.6.3 contains a prototype pollution vulnerability that allows attackers to alter object prototypes by supplying untrusted data to uneval. When the generated code is later evaluated, it creates objects with polluted prototypes, producing output data whose shape differs from the original input.
Vulnerability class: Prototype Pollution
Published .
CVSS v3 metric
CVSS v3 base score 4.4 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:L/I:L/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- GitHub Security Advisory (GHSA-8qm3-746x-r74r) (vendor-advisory)
- VulnCheck Advisory: Sveltejs devalue before 5.6.3 Prototype Pollution via uneval Output (third-party-advisory)
Frequently asked questions
- What is CVE-2026-123568?
- CVE-2026-123568 is a medium-severity vulnerability in Sveltejs Devalue, classified under Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution). CVSS score: 4.4/10. Published 2026-11-08.
- How severe is CVE-2026-123568?
- Medium severity. CVSS v3 base score is 4.4 out of 10.