CVE-2026-86060criticalunder attackCWE-88

CVE-2026-86060: critical vulnerability in Mikrotik RouterOS

SSH session privilege manipulation via a crafted username in Mikrotik RouterOS

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80Vexday Risk Score

Prioritize patching. It under exploitation confirmed by CISA, has an official Brazilian government alert and has a public proof of concept.

ssvc Actcvss 9.2epss 6.4%
from disclosure to weapon5 days
Published on NVDSep 5
1st PoC+5d
CISA KEV+5d
Official alert in Brazil

Brazil's federal government published an alert, recommendation or bulletin that cites this vulnerability.

Source: CTIR Gov (GSI) and CISC Gov.br, under the CC BY-ND 3.0 license.
Action required by CISAfederal deadline: 2026-09-13

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

In short

A flaw in Mikrotik RouterOS SSH login allows attackers to use specially crafted usernames to bypass security policies and gain unauthorized administrative privileges. An attacker can exploit this remotely without needing valid credentials, making it a serious threat to router security.

Technical detail

CVE-2026-86060 is an argument-handling vulnerability (CWE-88) in RouterOS SSH authentication that permits manipulation of the policy mask through malformed usernames containing prohibited characters. An unauthenticated attacker can reach the SSH login helper and escalate privileges by circumventing the trusted policy enforcement mechanism; the attack requires network access to the SSH service but no prior authentication.

Summary generated and translated by AI from the official description.
RouterOS contains an argument-handling flaw in the SSH login path involving usernames that begin with a prohibited character, allowing for the trusted RouterOS policy mask to be changed, leading to privilege escalation. Exploitation requires an unauthenticated SSH session to reach the RouterOS login helper.This issue was fixed in versions: 6.49.21 (Long-term), 7.23.4 (Long-term) and 7.24.2 (Stable)
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Affected products
Mikrotik · RouterOS
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