fast-toml through 0.5.4 Prototype Pollution via __proto__ Keys in Parsed TOML

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2021-48012
StatePUBLISHED
AssignerVulnCheck
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-12 21:17:06 UTC
Updated2026-10-26 18:17:04 UTC
Descriptionfast-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.

Risk And Classification

Primary CVSS: v4.0 8.8 HIGH from [email protected]

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:X/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: 0.004140000 probability, percentile 0.342610000 (date 2026-10-16)

Problem Types: CWE-1321 | CWE-1321 Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary8.8HIGHCVSS: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:X/C...
4.0CNACVSS8.8HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N
3.1[email protected]Secondary8.2HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L
3.1CNACVSS8.2HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
None
Confidentiality
None
Integrity
High
Availability
Low
Sub Conf.
None
Sub Integrity
None
Sub Availability
None

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:X/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

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
Low

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Gin-Quin Fast-toml affected 0.5.4 semver Not specified

References

ReferenceSourceLinkTags
www.vulncheck.com/advisories/fast-toml-through-0.5.4-prototype-pollution-via-pr... [email protected] www.vulncheck.com
github.com/Gin-Quin/fast-toml/pull/3 [email protected] github.com
github.com/Gin-Quin/fast-toml [email protected] github.com
github.com/Gin-Quin/fast-toml/issues/8 [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Abdulloh Nuriddinov (en)

CNA: Asjidkalam (en)

CNA: gnsehfvlr (en)

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