CVE-2026-123566

HIGH 7.5

Devalue before 5.9.3 CPU Amplification Denial of Service via uneval

CVSS Score

7.5

EPSS Score

0.0%

EPSS Percentile

0th

Sveltejs devalue before 5.9.3 contains a denial of service vulnerability that allows attackers to cause CPU amplification by supplying sparse arrays to uneval. Attackers who influence sparse values passed to uneval can force synchronous work proportional to the declared array length, blocking the event loop.

CWE	CWE-400
Vendor	sveltejs
Product	devalue
Published	Nov 8, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Affected Versions

sveltejs / devalue

0 < 5.9.3

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/sveltejs/devalue/security/advisories/GHSA-hx4r-w6wj-j8fg vulncheck.com: https://www.vulncheck.com/advisories/devalue-before-5.9.3-cpu-amplification-denial-of-service-via-uneval

Credits

elliott-with-the-longest-name-on-github