---
title: "CVE-2026-103903: MikroTik RouterOS - Authentication Bypass"
description: "MikroTik RouterOS contains an incorrect authorization vulnerability in the WinBox authentication flow, letting remote authenticated low-privilege users escalate to full administrative privileges by specifying a higher-privilege account, exploit requires valid low-privilege credentials."
url: https://panop.io/threat-heartbeat/CVE-2026-103903/
---

# CVE-2026-103903 MikroTik RouterOS - Authentication Bypass

MikroTik RouterOS contains an incorrect authorization vulnerability in the WinBox authentication flow, letting remote authenticated low-privilege users escalate to full administrative privileges by specifying a higher-privilege account, exploit requires valid low-privilege credentials.

CVSS base score 8.8 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Required

EPSS

0.41% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-103903)

## Details

Type

Authentication Bypass

Impact

Privilege Escalation

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Published

12 October 2026

Updated

15 October 2026

Weakness

[CWE-863](https://cwe.mitre.org/data/definitions/863.html)

## Vendor fix

Update to the latest MikroTik RouterOS version with the WinBox authentication fix.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-103903](https://nvd.nist.gov/vuln/detail/CVE-2026-103903)
- [https://br2sec.com/lv/resursi/2026-routeros-winbox-auth-bypass/](https://br2sec.com/lv/resursi/2026-routeros-winbox-auth-bypass/)
- [https://cvd.cert.lv/disclosed/vuln-all-709639748](https://cvd.cert.lv/disclosed/vuln-all-709639748)
- [https://forum.mikrotik.com/t/7-25rc1-testing-is-released/27352](https://forum.mikrotik.com/t/7-25rc1-testing-is-released/27352)
- [https://mikrotik.com/download/changelogs?channelFilter=stable&versionFilter=7.24.5](https://mikrotik.com/download/changelogs?channelFilter=stable&versionFilter=7.24.5)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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