CVE-2026-103903: MikroTik RouterOS WinBox: low-privilege user can get admin session

High 8.7 EPSS 0.4% MikroTik RouterOS

In the RouterOS 7 WinBox login flow, the first stage is checked against the attacker's own account while a separately supplied second-stage username decides which account's rights are installed. A user with any WinBox-capable login can therefore get a full administrative session as admin without its password and raise their own account's rights. It affects RouterOS 7.0 before 7.24.5; the fix is in 7.24.5, 7.23.8 and 7.25.

CVE-2026-103903CVE identifier
8.7CVSS 4.0 base score (high)
0.4%EPSS: chance of exploitation in the next 30 days (higher than 36% of CVEs)
2026-10-12published

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 7.0 before 7.24.5 (long-term 7.23.x before 7.23.8)

Fixed in:

RouterOS 7.24.5
RouterOS 7.23.8
RouterOS 7.25 (7.25rc1 and later)
Recommended as of 3 Nov 2026: 7.25 (stable) or 7.24.6 (long-term)

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
/user print   # every account whose group has the winbox policy can exploit this
/user group print

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. Until then, take the winbox policy away from groups used by low-privilege accounts (check with /user group print; a policy prefixed with ! is revoked) and disable accounts you do not need (/user disable <name>).
Allow WinBox only from management addresses: /ip service set winbox available-from=192.0.2.0/24 (address= before RouterOS 7.24), plus a firewall input-chain drop for TCP 8291 from other sources.

Look for signs of exploitation

Low-privilege accounts that suddenly belong to the full group, or admin sessions from a low-privilege user's usual address (/user print, /user active print, /log print where topics~"account").

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.