CVE-2026-123566
Devalue before 5.9.3 CPU Amplification Denial of Service via uneval
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.
Fixes and workarounds
Fix
devalue (npm): OSV reports a fixed version 5.9.3. Check the advisory for supported release branches.
Source: OSV GHSA-hx4r-w6wj-j8fgAffected products and versions
| Product | Versions | Authority |
|---|---|---|
| devalue sveltejs devalue
npm |
≥ 0; < 5.9.3 (affected, semver) 5.9.3 (unaffected, semver) Other versions: unaffected |
CNA: VulnCheck |
devaluedevalue
npm |
≥ 0; < 5.9.3 (affected, semver); OSV events: introduced 0; fixed 5.9.3Source events (semver)Other versions: unaffected |
OSV GHSA-hx4r-w6wj-j8fg |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 4.0 / 8.7 high |
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N | CNA: VulnCheck |
| 3.1 / 7.5 high |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | CNA: VulnCheck |
| 4.0 / 8.7 high |
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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 | NVD: [email protected] |
| 3.1 / 7.5 high |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | NVD: [email protected] |
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://github.com/sveltejs/devalue/security/advisories/GHSA-hx4r-w6wj-j8fgCNA: VulnCheck · vendor-advisory
- https://www.vulncheck.com/advisories/devalue-before-5.9.3-cpu-amplification-denial-of-service-via-unevalCNA: VulnCheck · third-party-advisory
- https://github.com/sveltejs/devalue/security/advisories/GHSA-hx4r-w6wj-j8fg[email protected]
- https://www.vulncheck.com/advisories/devalue-before-5.9.3-cpu-amplification-denial-of-service-via-uneval[email protected]
- https://github.com/advisories/GHSA-hx4r-w6wj-j8fgOSV / GitHub Security Advisories · advisory
- https://osv.dev/vulnerability/GHSA-hx4r-w6wj-j8fgOSV / GitHub Security Advisories · osv
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