CVE-2026-123566 json
Devalue before 5.9.3 CPU Amplification Denial of Service via uneval
published last mo. modified 2d ago also EUVD-2026-119451 , GHSA-hx4r-w6wj-j8fg
- cvss
- 7.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.3%
- EPSS 0.3% chance of exploitation in 30 days, percentile 28%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- npm devalue 5.9.3
- sveltejs devalue 5.9.3
Is CVE-2026-123566 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 2d ago
Exploit prediction
0.34% chance of exploitation in the next 30 days, higher than 28% of all scored CVEs (FIRST EPSS, 2026-11-11).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 8.7 | 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 | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| CNA | 4.0 | 8.7 | 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 |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| npm | devalue | <5.9.3 |
5.9.3 |
Affected products
- sveltejs devalue
Classification
References
-
github.com
/sveltejs/devalue/commit/6861dbbb7e548849e48bce718e88747a298f7250
web
-
github.com
/sveltejs/devalue/security/advisories/GHSA-hx4r-w6wj-j8fg
vendor-advisory, web, advisory
-
vulncheck.com
/advisories/devalue-before-5.9.3-cpu-amplification-denial-of-service-via-uneval
third-party-advisory
-
github.com
/sveltejs/devalue
package
-
github.com
/sveltejs/devalue/releases/tag/v5.9.3
web
Sources
- CVE List CVE-2026-123566
- GitHub Advisory GHSA-hx4r-w6wj-j8fg
- NVD CVE-2026-123566
- Maintainer advisory GHSA-hx4r-w6wj-j8fg
Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
The maintainers of sveltejs/devalue published their own advisory on GitHub. Reviewed sources take precedence over it.