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CVE-2026-123564VulnerabilityPublished

Sveltejs devalue from 1.0.0 before 5.9.3 contains a memory exhaustion flaw in uneval, whose generated code for sparse

Source GCVE Database

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Authoritative record:CVE-2026-123564· High 8.7

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

Data as of 8 Nov 2026, 06:36 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
  • >=1.0.0 <5.9.3
Fixed in
  • 5.9.3
npmdevaluepkg:npm/devalueOther threatsAffected
  • >=1.0.0 <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

If you cannot patch yet, avoid processing or accepting untrusted large sparse arrays in serialized data to reduce risk.

Description

Sveltejs devalue versions from 1.0.0 up to but not including 5.9.3 contain a memory exhaustion vulnerability in the uneval function. The flaw arises because the generated code for sparse arrays allocates memory proportional to the declared length of the array when evaluated. An attacker who can control a very large sparse array serialized by an application could cause memory exhaustion in the browser or runtime environment processing the output.

References

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