CVE-2026-86818
Description
A flaw was found in fast-uri, a Node.js URI parser. In versions 4.1.3 and 4.1.4, the mailto parser incorrectly handles percent-encoded query field names. This desynchronization between parsing and serialization allows an attacker to inject arbitrary recipients, subjects, or body content into mailto URIs. An application that re-serializes a validated mailto URI could unknowingly send emails to unintended recipients or with manipulated content.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4.8 | N/A | 4.8 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | Low | N/A | Low |
| Integrity Impact | Low | N/A | Low |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability
Technical Impact: Modify Application Data; Execute Unauthorized Code or Commands
An attacker could modify the structure of the message or data being sent to the downstream component, possibly injecting commands.
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