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CVE-2026-123566VulnerabilityPublished

Sveltejs devalue before 5.9.3 contains a denial of service vulnerability that allows attackers to cause CPU

Source GCVE Database

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Authoritative record:CVE-2026-123566· High 8.7

Not known to be exploited · CVSS 8.7 High : upgrade to 5.9.3 soon.

Data as of 8 Nov 2026, 06:47 UTC

CVSS 4.0 base score
8.7High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (VulnCheck)CVSS 4.08.7
CNA (VulnCheck)CVSS 3.17.5
Patch
Available – fixed in 5.9.3
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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 8 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 7 Nov 2026.

What to do

Upgrade devalue to 5.9.3.

Affected software

ProductAffectedFixed in
sveltejsdevalueAffected
  • <5.9.3
Fixed in
  • 5.9.3
npmdevaluepkg:npm/devalueOther threatsAffected
  • <5.9.3
Fixed in
  • 5.9.3

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade to Sveltejs devalue version 5.9.3 or later, where this vulnerability is fixed. No other mitigation guidance is provided.

Description

Sveltejs devalue versions before 5.9.3 have a denial of service vulnerability. Attackers can supply sparse arrays to the uneval function, causing CPU amplification and blocking the event loop by forcing synchronous work proportional to the array's declared length.

References

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