Mikrotik Routeros Authentication Bypass Vulnerability ((hot))

Note: If you are referring to a different or newer CVE (e.g., from 2024/2025), please check MikroTik’s latest security advisory. As of my last knowledge update, CVE-2023-30799 is the critical authentication bypass affecting WinBox and HTTP.

The vulnerability stems from improper validation of user session cookies and request headers. By crafting a malicious request with a specially manipulated cookie or HTTP header, an attacker can trick the service into believing the request is coming from an already authenticated administrator. In simpler terms: the door has a lock, but the lock can be opened with a plastic card instead of a key.

At 00:17 UTC, an automated scanner found the bypass. By 00:19, a script sent:
POST /login HTTP/1.1
username=admin%00&password=anything mikrotik routeros authentication bypass vulnerability

Also, I want to highlight that I am not a security expert, and this post is not an exhaustive analysis of the vulnerability, but rather a general overview. For a more detailed analysis, I recommend checking the Mikrotik security advisory and other reliable sources.

The Mechanism: Attackers could modify a single byte in a Session ID request to the Winbox server on port 8291. Note: If you are referring to a different or newer CVE (e

in a request related to a Session ID, a remote attacker could trick the router into thinking they were already authenticated.

  • Host indicators:

    The cost of ignoring this vulnerability is no longer a potential data breach—it is an inevitable botnet infection. Patch now or plan your incident response later. In the world of network security, that choice is already made for you. Host indicators: The cost of ignoring this vulnerability

    Critical Alert: MikroTik RouterOS Authentication Bypass Vulnerability (CVE-2022-4537 & CVE-2022-47934)

    Introduction: The Gateway Under Siege

    MikroTik’s RouterOS powers millions of routers, ISPs, and enterprise gateways worldwide. Its flexibility and low cost have made it a staple of global networking. However, in late 2022 and early 2023, security researchers uncovered a catastrophic flaw: an authentication bypass vulnerability that allowed unauthenticated attackers to gain administrative control over affected devices.