# CVE-2026-103903: MikroTik RouterOS WinBox incorrect authorization in authentication

Source: https://junglewise.ai/threats/cve-2026-103903-an-incorrect-authorization-vulnerability-in-the-winbox  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-12. Updated: 2026-10-16  
License: CC BY 4.0 with a link back

CVE-2026-103903 · Severity: high · CVSS 8.8 · Published 2026-10-12

MikroTik RouterOS is network management software used to configure routers and network devices. A flaw in the WinBox authentication system allows a low-privilege user with read-only access to escalate themselves to full administrator without knowing the admin password. An attacker can gain complete control of the router, potentially redirecting network traffic, stealing data, or disrupting network service.

Technologies: [MikroTik RouterOS](https://junglewise.ai/threats/technologies/routeros). Vendors: [MikroTik](https://junglewise.ai/threats/vendors/mikrotik).

## Quick answers

**Is CVE-2026-103903 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-103903 being exploited in the wild.

**How severe is CVE-2026-103903?** High severity, with a CVSS score of 8.8, published 12 October 2026.

**Which products and versions are affected?** MikroTik RouterOS before 7.24.5.

**Is there a fix for CVE-2026-103903?** Yes: fixed in RouterOS 7.24.5, 7.25rc1 and later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-103903 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-103903?** Check whether you run MikroTik RouterOS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in RouterOS 7.24.5, 7.25rc1 and later

## Technical details

An incorrect authorization vulnerability in the WinBox authentication flow decouples the verified account from the account whose privileges are granted. The EC-SRP stage-one challenge and proof are verified against the attacker's low-privilege account, but a stage-two username parameter is independently used to install the target account's authorization policy. A network-based authenticated attacker with low-privilege credentials can complete authentication as themselves, then inject a high-privilege username to obtain that account's full privileges without knowing its password.

## Affected products

- MikroTik RouterOS before 7.24.5

## Timeline

- 2026-09-22: disclosed
- 2026-10-12: patched: CVE-2026-103903 published; fixes available since 2026-09-22

## References

- [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)

## Related threats

- [MikroTik RouterOS session token replay authentication bypass in WebFig](https://junglewise.ai/threats/cve-2026-89035-mikrotik-routeros-through-7-24-5-contains-a-session-token-replay)
- [MikroTik RouterOS integer overflow in ipt_SAME module](https://junglewise.ai/threats/cve-2026-112158-a-weakness-has-been-identified-in-mikrotik-routeros-up-to-6-40-5)
- [MikroTik RouterOS integer underflow](https://junglewise.ai/threats/cve-2026-84411-mikrotik-routeros)
- [MikroTik RouterOS improper input validation in BGP labelled-VPN NLRI](https://junglewise.ai/threats/cve-2026-93345-mikrotik-routeros-before-7-25beta4-contains-an-improper-input)
- [MikroTik firmware cleartext credential storage](https://junglewise.ai/threats/cve-2025-56566-mikrotik-firmware-cleartext-credential-storage)