CVE-2026-84411: MikroTik RouterOS web interface: one request can run code as root

Critical 9.3 EPSS 0.9% MikroTik RouterOS

An integer underflow in HTTP request body handling in the RouterOS web management service (the WebFig service on the www and www-ssl ports) is reachable before login. A single crafted request from an unauthenticated attacker can crash the service or run code on the router with full privileges (CVSS 9.8). It affects RouterOS before 7.24, including RouterOS 6; MikroTik fixed it in 7.24, 7.23.8 and 6.49.23. No exploitation was known when CISA published its advisory on 29 September 2026.

CVE-2026-84411CVE identifier
9.3CVSS 4.0 base score (critical)
0.9%EPSS: chance of exploitation in the next 30 days (higher than 59% of CVEs)
2026-10-02published

What do these terms mean? CVE · CVSS score · exploited (KEV) · EPSS · backported fix · all terms

What to do now

Check whether you run MikroTik RouterOS and which version (commands below).
Install the fixed version for your system: see “Patch it” below.
Installing a RouterOS update always reboots the router. On RouterBOARD hardware, run /system routerboard upgrade afterwards and reboot a second time so the matching RouterBOOT firmware is loaded. Plan for two short outages and make sure you have out-of-band or local access in case the router does not come back.
If you cannot patch today, apply the temporary mitigation below and patch as soon as possible.

Affected and fixed versions

Affected:

RouterOS before 7.24 (including RouterOS 6), where www or www-ssl is reachable by the attacker
Long-term 7.23.x before 7.23.8
RouterOS 6 before 6.49.23

Fixed in:

RouterOS 7.24 (stable)
RouterOS 7.23.8 (long-term)
RouterOS 6.49.23
Recommended as of 3 Nov 2026: 7.25 (stable), 7.24.6 (long-term) or 6.49.23

Am I affected?

/system resource print   # version, architecture-name, board-name
/system package update print   # channel, installed-version, latest-version
/system routerboard print   # current-firmware vs upgrade-firmware (not on CHR/x86)
/ip service print   # which management services are enabled, and from where
/ip service print where name~"www"

Patch it

Use the commands for your system. Distribution packages often keep an older version number with the fix backported, so compare with the fixed package versions in the table below, not only with the upstream version.

Built from source

# RouterOS CLI (works on v6 and v7; v7 also accepts /system/package/update/...)
# Current releases as of 3 Nov 2026: 7.25 (stable), 7.24.6 (long-term), 6.49.23 (RouterOS 6)
/system backup save name=pre-update
/export file=pre-update
/system package update set channel=long-term   # or stable
/system package update check-for-updates
/system package update print   # status should say: New version is available
/system package update install   # downloads, installs and REBOOTS the router
# after it is back up:
/system resource print   # confirm the new version
/system routerboard upgrade   # RouterBOARD only: new RouterBOOT firmware
/system reboot   # REBOOTS again to load the firmware

General update steps for every system are on the Linux and Unix & BSD pages; after updating, see which services to restart.

If you cannot patch yet

Updating is the fix. If you do not use WebFig, disable it: /ip service disable www,www-ssl
Otherwise allow it only from trusted addresses (/ip service set www available-from=192.0.2.0/24; address= before RouterOS 7.24) and keep the default firewall rules that block the web interface from the WAN side.
Use a VPN such as WireGuard for remote access instead of opening management ports (MikroTik).

Look for signs of exploitation

The web service crashing or restarting without reason, and unknown users, scripts or scheduler entries afterwards (/user print, /system script print, /system scheduler print).

Related vulnerabilities

Sources

Page generated automatically from official sources on 2026-11-03 18:05 UTC and reviewed by an editor. Always confirm with your vendor's advisory.