Authorization Flaw in MikroTik RouterOS (CVE-2026-103903)
Summary
Vulnerability in MikroTik RouterOS (CVE-2026-103903). Successful exploitation can lead to full system takeover.
Original description
The description as published by the source.
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.
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-103903 has been found in MikroTik RouterOS.
Successful exploitation can lead to full system takeover. CVSS score: 8.8/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "MikroTik RouterOS CVE-2026-103903" on the vendor's site.
CVE-2026-103903 (MikroTik RouterOS) — CWE-863 / CVSS v3 8.8
Attack vector: remote (network-reachable) / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Incorrect authorization (CWE-863) exists in MikroTik RouterOS.
Check the vendor advisory for the affected versions of MikroTik RouterOS.
Severity: High (CVSS 8.8/10). Successful exploitation can lead to full system takeover.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで MikroTik RouterOS を使っているサービスとバージョンを洗い出す。
-
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
References
- web nvd.nist.gov
- web br2sec.com
- web cvd.cert.lv
- web forum.mikrotik.com
- web mikrotik.com
- web github.com
- web br2sec.com