fast-toml through 0.5.4 contains a prototype pollution vulnerability that allows attackers to modify Object.prototype by supplying TOML containing __proto__, constructor or prototype key segments. Attackers can pass [__proto__] or [constructor.prototype] table headers or __proto__.x dotted keys to parse() to pollute all objects, causing denial of service or authorization bypass.

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact High

Vulnerable System Availability Impact Low

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact High

Availability Impact Low

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
Gin-Quin fast-toml unaffected
Version Status Constraints
0 affected ≤ 0.5.4

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Project Subscriptions

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Advisories

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Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/Gin-Quin/fast-toml cve-icon cve-icon
https://github.com/Gin-Quin/fast-toml/issues/8 cve-icon cve-icon
https://github.com/Gin-Quin/fast-toml/pull/3 cve-icon cve-icon
https://www.vulncheck.com/advisories/fast-toml-through-0.5.4-prototype-pollution-via-proto-keys-in-parsed-toml cve-icon cve-icon
History

Mon, 12 Oct 2026 21:00:00 +0000

Type Values Removed Values Added
Description fast-toml through 0.5.4 contains a prototype pollution vulnerability that allows attackers to modify Object.prototype by supplying TOML containing __proto__, constructor or prototype key segments. Attackers can pass [__proto__] or [constructor.prototype] table headers or __proto__.x dotted keys to parse() to pollute all objects, causing denial of service or authorization bypass.
Title fast-toml through 0.5.4 Prototype Pollution via __proto__ Keys in Parsed TOML
Weaknesses CWE-1321
References
Metrics cvssV3_1

{'score': 8.2, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L'}

cvssV4_0

{'score': 8.8, 'vector': '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'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-10-12T20:55:05.966Z

Reserved: 2026-10-12T19:37:38.614Z

Link: CVE-2021-48012

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-12T21:17:06.057

Modified: 2026-10-12T21:17:06.057

Link: CVE-2021-48012

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-12T22:30:07Z

Weaknesses