LabOne Web Server Suffers Arbitrary File Read Flaw
The National Vulnerability Database has identified CVE-2026-6903, a critical vulnerability in the LabOne Web Server. This flaw stems from insufficient input validation, allowing unauthenticated attackers to read any file accessible by the operating system user running the LabOne software. This means sensitive configuration files, user data, or even system credentials could be exposed.
Compounding the risk, the Web Server’s inadequate cross-origin request restrictions mean an attacker could trick a user into visiting a malicious website, thereby triggering the file access from their browser. The CVSS score of 7.5 (HIGH) underscores the severity. Crucially, this vulnerability only affects installations where the LabOne Web Server is active; API-only usage remains unaffected.
What This Means For You
- If your organization uses LabOne software and its Web Server component is enabled, you must patch this immediately. Prioritize systems where LabOne runs with elevated privileges, as this significantly increases the potential impact of arbitrary file reads. Audit access logs for any unusual file access patterns that might indicate prior compromise.
Related ATT&CK Techniques
🛡️ Detection Rules
3 rules · 6 SIEM formats3 detection rules auto-generated for this incident, mapped to MITRE ATT&CK. Sigma YAML is free — export to any SIEM format via the Intel Bot.
CVE-2026-6903 - LabOne Web Server Arbitrary File Read
Indicators of Compromise
| ID | Type | Indicator |
|---|---|---|
| CVE-2026-6903 | Information Disclosure | LabOne Web Server - insufficient input validation in file access functionality |
| CVE-2026-6903 | Information Disclosure | LabOne Web Server - read arbitrary files on host system |
| CVE-2026-6903 | CSRF | LabOne Web Server - insufficient restriction of cross-origin requests |
Written by SCW Vulnerability Desk
Source & Attribution
| Source Platform | NVD |
| Channel | National Vulnerability Database |
| Published | April 23, 2026 at 13:16 UTC |
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