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CVE-2026-123567

6.3 mediumEPSS 0.2%Fix available

Medium (6.3) in sveltejs devalue. EPSS 0.2% estimated probability of exploitation activity in the next 30 days. Fixed in devalue 5.6.4.

On this page
Sveltejs devalue before 5.6.4 contains a prototype injection vulnerability that allows attackers to inject __proto__ own properties into objects returned by devalue.parse and devalue.unflatten. Attackers can supply crafted serialized input that, when downstream code merges results via Object.assign, alters the target object's prototype.

Severity

CVSS 4.0

6.3 medium
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

CVSS 3.1

3.7 low
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
EPSS
0.2% estimated probability of exploitation activity in the next 30 days; 15th percentile. Scored 2026-11-10. A forecast for this CVE across the internet, not for your own systems.
CWE
CWE-1321 Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution)
Published
NVD analysis
Awaiting analysis
Record from
the NVD, synced

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Affected

Versions

From the CNA's record in the CVE List.

ProductAffected
sveltejs devaluebefore 5.6.4

Packages (OSV)

AdvisoryEcosystemPackageAffectedFixed in
GHSA-mwv9-gp5h-frr4npmdevalue>=4.0.0 <5.6.45.6.4

Attack patterns (CAPEC)

  • CAPEC-1 Accessing Functionality Not Properly Constrained by ACLs Likelihood: High · Severity: High
  • CAPEC-77 Manipulating User-Controlled Variables Likelihood: High · Severity: Very High
  • CAPEC-180 Exploiting Incorrectly Configured Access Control Security Levels Likelihood: High · Severity: Medium

The attack patterns MITRE's CAPEC relates to this record's weaknesses, as MITRE names them. Credits.

References

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