Weakness in Mailto Header Handler of garycourt uri-js by garycourt
CVE-2026-103387

5.3MEDIUM

Key Information:

Vendor

Garycourt

Status
Uri-js
Vendor
CVE Published:
30 September 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2026-103387?

A weakness exists in the Mailto Header Handler of garycourt's uri-js library up to version 4.4.1, specifically in the URI.parse function located in src/schemes/mailto.ts. This vulnerability can lead to uncaught exceptions due to improper handling of parsed arguments. An attacker may exploit this remotely, and the details of the exploit are publicly available. Despite being reported to the project earlier, there has been no response or action taken to address this issue.

Affected Version(s)

uri-js 4.4.0

uri-js 4.4.1

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2026-103387 - Proof of Concept

References

https://vuldb.com/vuln/412124
vdb-entrytechnical-description
https://vuldb.com/vuln/412124/cti
signaturepermissions-required
https://vuldb.com/cve/CVE-2026-103387
third-party-advisory

CVSS V4

Score:
5.3
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
Unknown

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

Credit

Yu Bao from PayPal Cyber Security Team (VulDB User)
VulDB CNA Team
.