CVE-2026-123561
Sveltejs devalue before 5.9.3 __proto__ Rejection Bypass via Property-Key Coercion
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.
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
- None
- Integrity
- Low
- Availability
- None
What each source reports
CVE List Score used
Sveltejs devalue before 5.9.3 __proto__ Rejection Bypass via Property-Key Coercion
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.
- Record
CVE-2026-123561- CVSS 4.0
- 6.3 Medium
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N - CVSS 3.1
- 3.7 Low
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N - Weakness
- CWE-1321
- Updated
- 2026-11-08
EUVDEUVD-2026-119446
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.
- Record
EUVD-2026-119446- CVSS 4.0
- 6.3 Medium
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N - Updated
- 2026-11-08
GitHub AdvisoriesGHSA-2fcf-p6fg-p2wf
devalue before 5.9.3 allows malformed null-prototype object keys to bypass parse's __proto__...
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.
- Record
GHSA-2fcf-p6fg-p2wf- CVSS 4.0
- 6.3 Medium
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - CVSS 3.1
- 3.7 Low
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N - Weakness
- CWE-1321
- Updated
- 2026-11-08
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| published | EUVD | |
| aliases, references | GitHub Advisories | |
| aliases, published | EUVD | |
| first indexed | CVE List |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-123561 is a medium vulnerability (CVSS 6.3) in Sveltejs Devalue, published November 8, 2026. No source lists public exploit code. No source names a fixed version.