MikroTik RouterOS WinBox split-principal authentication bypass allows privilege escalation
Summary
| CVE | CVE-2026-103903 |
|---|---|
| State | PUBLISHED |
| Assigner | ENISA |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-10-12 11:17:09 UTC |
| Updated | 2026-10-16 17:25:57 UTC |
| 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. |
Risk And Classification
Primary CVSS: v4.0 8.7 HIGH from a6d3dc9e-0591-4a13-bce7-0f5b31ff6158
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS: 0.004150000 probability, percentile 0.342870000 (date 2026-10-16)
Problem Types: CWE-863 | CWE-863 CWE-863 Incorrect Authorization
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | a6d3dc9e-0591-4a13-bce7-0f5b31ff6158 | Secondary | 8.7 | HIGH | 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/E:X/C... |
| 4.0 | CNA | CVSS | 8.7 | HIGH | 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 |
| 3.1 | a6d3dc9e-0591-4a13-bce7-0f5b31ff6158 | Secondary | 8.8 | HIGH | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
| 3.1 | CNA | CVSS | 8.8 | HIGH | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
CVSS v4.0 Breakdown
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS v3.1 Breakdown
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Vendor Declared Affected Products
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| cvd.cert.lv/disclosed/vuln-all-709639748 | a6d3dc9e-0591-4a13-bce7-0f5b31ff6158 | cvd.cert.lv | |
| forum.mikrotik.com/t/7-25rc1-testing-is-released/27352 | a6d3dc9e-0591-4a13-bce7-0f5b31ff6158 | forum.mikrotik.com | |
| mikrotik.com/download/changelogs | a6d3dc9e-0591-4a13-bce7-0f5b31ff6158 | mikrotik.com | |
| br2sec.com/lv/resursi/2026-routeros-winbox-auth-bypass | a6d3dc9e-0591-4a13-bce7-0f5b31ff6158 | br2sec.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Additional Advisory Data
Solutions
CNA: Upgrade to RouterOS 7.24.5 stable, 7.25rc1 testing, or a later vendor release containing the fix.
Workarounds
CNA: Until upgrade, restrict the WinBox service to trusted management addresses, remove the winbox policy from low-privilege accounts, or disable WinBox. These measures reduce reachability but do not replace the fix.