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CVE-2026-123561VulnerabilityPublished

devalue before 5.9.3 allows malformed null-prototype object keys to bypass parse's __proto__ rejection through

Source GCVE Database

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Authoritative record:CVE-2026-123561· Medium 6.3

Not known to be exploited · CVSS 6.3 Medium : upgrade to 5.9.3 when convenient.

Data as of 8 Nov 2026, 06:47 UTC

CVSS 4.0 base score
6.3Medium
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (VulnCheck)CVSS 4.06.3
CNA (VulnCheck)CVSS 3.13.7
Patch
Available – fixed in 5.9.3
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/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

A fix is available in devalue version 5.9.3 and later. Users should upgrade to version 5.9.3 or newer to remediate this vulnerability. No other mitigation actions are indicated by the vendor advisory or source data.

Description

A vulnerability in devalue versions before 5.9.3 allows attackers to bypass the __proto__ property rejection during parsing by using malformed null-prototype object keys through property-key coercion. This is an incomplete fix related to a previous advisory (GHSA-mwv9-gp5h-frr4). Although attackers can craft payloads that produce objects with a __proto__ own property, this alone does not lead to prototype pollution.

References

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