CVE-2026-8657

High

Published: 16 May 2026

Published

16 May 2026

Modified

19 May 2026

KEV Added

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Patch

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CVSS Score v4 7.8 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Score 0.0037 28.9th percentile

Risk Priority 55 floored blend · peak EPSS

Summary

CVE-2026-8657 is a high-severity Prototype Pollution (CWE-1321) vulnerability in Snyk (inferred from references). Its CVSS base score is 7.8 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 28.9th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

EU & UK References

🇪🇺 ENISA EUVD: EUVD-2026-30670

Vulnerability details

Versions of the package jsondiffpatch before 0.7.6 are vulnerable to Prototype Pollution via the jsondiffpatch.patch() and jsondiffpatch/formatters/jsonpatch.patch() APIs. An attacker can perform prototype pollution by supplying crafted delta or JSON Patch documents, as attacker-controlled property names and path segments are…

used to traverse and modify objects without restricting access to special properties like __proto__ or constructor.prototype, allowing modification of Object.prototype.

CWE(s): CWE-1321

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

Why these techniques?

Prototype pollution via crafted untrusted input to patch APIs directly enables exploitation of applications accepting such data (e.g., web services).

Confidence: MEDIUM · MITRE ATT&CK Enterprise v19.0

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CVE-2026-29063Shared CWE-1321

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CVE-2026-45302Shared CWE-1321

CVE-2025-61140Shared CWE-1321

CVE-2024-57077Shared CWE-1321

CVE-2026-34221Shared CWE-1321

CVE-2026-35209Shared CWE-1321

CVE-2026-33994Shared CWE-1321

CVE-2024-38988Shared CWE-1321

Affected Assets

Snyk

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inferred from references and description; NVD did not file a CPE for this CVE

Mitigating Controls

No mitigating controls mapped yet. The per-CVE control annotator has not reached this CVE.