CVE-2026-103903
MikroTik RouterOS WinBox split-principal authentication bypass allows privilege escalation
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.
INFO
Published Date :
Oct. 12, 2026, 11:17 a.m.
Last Modified :
Oct. 12, 2026, 11:17 a.m.
Remotely Exploit :
Yes !
Source :
a6d3dc9e-0591-4a13-bce7-0f5b31ff6158
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | a6d3dc9e-0591-4a13-bce7-0f5b31ff6158 | ||||
| CVSS 3.1 | HIGH | MITRE-CVE | ||||
| CVSS 4.0 | HIGH | a6d3dc9e-0591-4a13-bce7-0f5b31ff6158 | ||||
| CVSS 4.0 | HIGH | a6d3dc9e-0591-4a13-bce7-0f5b31ff6158 |
Solution
- Apply the latest RouterOS security updates.
- Review and restrict WinBox access.
- Monitor authentication logs for suspicious activity.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-103903.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-103903 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-103903
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-103903 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-103903 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by a6d3dc9e-0591-4a13-bce7-0f5b31ff6158
Oct. 12, 2026
Action Type Old Value New Value Added 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. Added CVSS V4.0 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 Added CVSS V3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Added CWE CWE-863 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/103xxx/CVE-2026-103903.json">CVE-2026-103903</a> Added Reference https://br2sec.com/lv/resursi/2026-routeros-winbox-auth-bypass/ Added Reference https://cvd.cert.lv/disclosed/vuln-all-709639748 Added Reference https://forum.mikrotik.com/t/7-25rc1-testing-is-released/27352 Added Reference https://mikrotik.com/download/changelogs?channelFilter=stable&versionFilter=7.24.5