CVE-2026-123561
Sveltejs devalue before 5.9.3 __proto__ Rejection Bypass via Property-Key Coercion
CVSS Score
3.7
EPSS Score
0.0%
EPSS Percentile
0th
devalue before 5.9.3 allows malformed null-prototype object keys to bypass parse's __proto__ rejection through property-key coercion, an incomplete fix for GHSA-mwv9-gp5h-frr4. Attackers can supply crafted payloads that yield objects with a __proto__ own property, which alone does not cause prototype pollution.
| CWE | CWE-1321 |
| Vendor | sveltejs |
| Product | devalue |
| Published | Nov 8, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None
Affected Versions
sveltejs / devalue
0 < 5.9.3
References
Credits
elliott-with-the-longest-name-on-github