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  4. CVE 2026 123567 sveltejs devalue before 564 prototype injection
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Back to active CVEs
Medium · CVSS 6.3CVE-2026-123567

Sveltejs devalue before 5.6.4 Prototype Injection via parse and unflattenCVE-2026-123567

Answer in brief

CVE-2026-123567 records a Medium severity (CVSS 6.3) vulnerability in Sveltejs devalue before 5.6.4 Prototype Injection via parse and unflatten. The current sources do not mark it as known exploited. The current feed maps sveltejs/devalue (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Nov 8, 2026Updated Nov 8, 2026Source checked Nov 8, 2026First seen by HOL Nov 8, 2026Material review Nov 8, 2026
Upstream Advisory

Key facts

Risk
Medium · CVSS 6.3
Exploitation
Not marked as known exploited
Affected software
1 mapped package or product
Fix availability
Available

Why this deserves its current priority

CVSS is 6.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps sveltejs/devalue (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
PackageAffected rangeFixed version
sveltejs/devaluegeneric>=0 <5.6.45.6.4

Recommended response

  1. 1Check inventory. Check lockfiles and deployed manifests for sveltejs/devalue.
  2. 2Review the reported fix. Update sveltejs/devalue to 5.6.4 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

  1. Published upstream

    Nov 8, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  2. Source modified

    Nov 8, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  3. First seen by HOL

    Nov 8, 2026

Sources and claim methodology

  • GitHub security advisorygithub.com
  • Source referencevulncheck.com
Upstream source description

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.

Quoted source text, attributed separately from HOL analysis.

Related CVEs

  • Sveltejs devalue before 5.6.3 Prototype Pollution via uneval OutputSame sveltejs/devalue package
  • Devalue before 5.6.3 Denial of Service via Sparse Array SerializationSame sveltejs/devalue package

Record context

Vulnerability class
Vulnerability
EPSS
Not reported
CWE IDs
CWE-1321
Source
CVE List V5
Source checked
Nov 8, 2026
References
2 linked sources
Open source record