High · CVSS 8.7CVE-2026-103903

MikroTik RouterOS WinBox split-principal authentication bypass allows privilege escalationCVE-2026-103903

Answer in brief

CVE-2026-103903 records a High severity (CVSS 8.7) vulnerability in MikroTik RouterOS WinBox split-principal authentication bypass allows privilege escalation. The current sources do not mark it as known exploited. The current feed maps MikroTik/RouterOS (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 12, 2026Updated Oct 12, 2026Source checked Oct 12, 2026First seen by HOL Oct 12, 2026Material review Oct 12, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 8.7
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 8.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps MikroTik/RouterOS (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
MikroTik/RouterOSgeneric	>=7.0.0 <7.24.5	7.24.5

Recommended response

Check inventory. Check lockfiles and deployed manifests for MikroTik/RouterOS.
Review the reported fix. Source-reported solution: Upgrade to RouterOS 7.24.5 stable, 7.25rc1 testing, or a later vendor release containing the fix.

Evidence timeline and material changes

Published upstream
Oct 12, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 12, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Oct 12, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.