Yayson: Prototype pollution in the Store/LegacyStore deserialization
CVSS score
9.1
EPSS probability
%0.8
Risk score
0.1
Published
1 mo ago
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Vulnerability description
DayBreach CVE AI Research
CVE-2026-61534 has vendor, distribution, patch and security-source records on file. We can compare them and prepare an explanation linked to the evidence.
Yayson is a library for serializing and reading JSON API data in JavaScript. Prior to 4.3.0, Store and LegacyStore use attacker-controlled JSON:API type, id, and relationship names as keys in plain-object lookup tables in src/yayson/store.ts and src/yayson/legacy-store.ts. A document whose type is __proto__ causes model-cache writes to modify Object.prototype, with the attacker controlling the polluted property name through id and its value through attributes. The malicious type can also be supplied by an included resource, and LegacyStore is reachable when a configured types mapping resolves to __proto__. Unsafe relationship names including __proto__, constructor, and prototype provide additional document-derived member paths. The resulting process-wide prototype pollution can cause denial of service and logic corruption; authorization bypass or code execution depends on suitable gadgets in the consuming application. This issue is fixed in version 4.3.0.
IMPACT: Affected Products and Software
RED HAT CSAF/VEX: Product Impact Check
SCORING: CVSS from Multiple Sources
CVSS Scores
The Common Vulnerability Scoring System is a standardised framework for assessing the severity of vulnerabilities in software and systems. We collect and display CVSS scores from several sources for each CVE.
| SCORE | VERSION | SEVERITY | VECTOR | SOURCE |
|---|---|---|---|---|
| 9.1 | CVSS V3_1 | CRITICAL | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H | CVE CNA |
| 9.1 | CVSS V31 | CRITICAL | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H | NVD |
| 9.1 | CVSS 3.x | — | Vector not published | GitHub Advisory |
| 0.0 | CVSS 4.0 | — | Vector not published | GitHub Advisory |
Patch and Remediation Guide
Solution & Remediation Advisory
1 doğrulanmış yama veya düzeltilmiş sürüm kanıtı bulundu.
4.3.0GitLab Advisory düzeltilmiş sürüm: 4.3.0
Upgrade to version 4.3.0 or above.
Upgrade to version 4.3.0 or above.
Public exploit and active exploitation status
Verified exploit intelligence
No verified public PoC, exploit repository or Metasploit module has been found for this CVE yet.
Weakness Classification and Attack Patterns (CWE & CAPEC)
CWE - Common Weakness Enumeration
While CVE identifies specific instances of vulnerabilities, CWE categorises the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-61534 is associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-61534 weaknesses.
Attack Vector and Accessibility
Official Sources and Advisories
Similar Vulnerabilities
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