CVE-2021-48012

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

HIGH
8.2
CVSS Score
Published: October 12, 2026 at 08:55 PM UTC
Updated: October 26, 2026 at 06:17 PM UTC
1 product affected across 1 vendorFast Toml

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Severity
HIGH8.2
Exploit prediction
EPSS 0.4%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

8.2HIGHVulnCheck
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
HIGH
Availability
LOW
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-1321

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