CVE-2026-61534 Yayson - Prototype Pollution

Yayson < 4.3.0 contains a prototype pollution vulnerability caused by attacker-controlled JSON:API type, id, and relationship names used as keys in object lookup tables, letting attackers cause process-wide prototype pollution, exploit requires crafted JSON:API documents.

CVSS base score 9.1 /10
Critical
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
EPSS
0.84% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Prototype Pollution
Impact
Denial Of Service, Privilege Escalation, Remote Code Execution
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Published
14 September 2026
Updated
15 October 2026
Weakness
CWE-1321

Vendor fix

Update to version 4.3.0 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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