garycourt uri-js Mailto Header mailto.ts URI.parse uncaught exception (CVE-2026-103387) | HOL Guard CVE

Medium · CVSS 5.3CVE-2026-103387

garycourt uri-js Mailto Header mailto.ts URI.parse uncaught exception

Answer in brief

CVE-2026-103387 records a Medium severity (CVSS 5.3) vulnerability in garycourt uri-js Mailto Header mailto.ts URI.parse uncaught exception. The current sources do not mark it as known exploited. The current feed maps garycourt/uri-js (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 30, 2026Updated Sep 30, 2026Source checked Sep 30, 2026First seen by HOL Sep 30, 2026Material review Sep 30, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 5.3
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Not reported

Why this deserves its current priority

CVSS is 5.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps garycourt/uri-js (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
garycourt/uri-jsgeneric	4.4.0 \|\| 4.4.1	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for garycourt/uri-js.
Review the reported fix. Monitor this advisory for an available fix and review any installs of the affected package.

Evidence timeline and material changes

Published upstream
Sep 30, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 30, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 30, 2026

Sources and claim methodology

Upstream source description

A weakness has been identified in garycourt uri-js up to 4.4.1. This affects the function URI.parse of the file src/schemes/mailto.ts of the component Mailto Header Handler. This manipulation of the argument to causes uncaught exception. The attack may be initiated remotely. The exploit has been made available to the public and could be used for attacks. The project was informed of the problem early through an issue report but has not responded yet.

Quoted source text, attributed separately from HOL analysis.