Vulnerability in MikroTik RouterOS

[ Why it matters ]Priority signals

• Critical severity: CVSS 9.8

[ Description ]Official description

The web management service in affected RouterOS versions contains an integer underflow in its HTTP request body handling that is reachable before authentication. This can be leveraged by an unauthenticated network attacker to achieve arbitrary code execution as root, or to cause a denial of service, using a single crafted request.

[ Fixes ]Fixes and patches

No fix or interim patch is linked from our sources yet. Check the vendor references below and limit exposure of affected systems until a fix is available.

[ Advisories ]Government CERT advisories

• BSI CERT-Bund29 Sep 2026WID-SEC-2026-3661

  MikroTik RouterOS: Vulnerability allows code execution and denial of service Translated from German

  CVE-2026-84411

[ References ]References

• github.com/cisagov/CSAF/blob/develop/csaf_files/OT/white/2026/icsa-26-272-06.json
• mikrotik.com/download
• www.cisa.gov/news-events/ics-advisories/icsa-26-272-06