CVE-2026-67277KEV · OVERDUECWE-306

MikroTik RouterOS Missing Authentication for Critical Function Vulnerability

High · published September 6, 2026

Patch now

Confirmed exploited, and the score agrees

CVSS calls it high at 8.2. It is confirmed in active exploitation. It sits in the 75.1th percentile for exploit probability.

41
days past CISA
deadline
CVSS v3.1
8.2
EPSS
2%
Percentile
75.1
In the wild
Confirmed
What it is

RouterOS accepts a "related" btest connection before the corresponding primary session has completed authentication. An unauthenticated client can use this state to start an IPv4 UDP test. With "random-data=false", the sender transmits an uninitialized tail from a kernel packet buffer. A separate unchecked, inverted packet-size interval causes unsigned integer underflow, anomalously large fragmented output, and can restart the RouterOS kernel.

This issue was fixed in versions: 6.49.21 (Long-term), 7.23.4 (Long-term) and 7.24.2 (Stable)

The record
Technical detail
CVSS v3.1
8.2 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
CVSS v4.0
8.8 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N
EPSS
0.01560 · 75.1th percentile
Weakness
CWE-306 · Missing Authentication for Critical Function
Published
2026-09-06T00:17Z
KEV added
2026-09-10 · due 2026-09-13
Affected products (3)
ProductVersionsFixed in
mikrotik/routeros≥ 6.0, < 6.49.216.49.21
mikrotik/routeros≥ 7.0, < 7.23.47.23.4
mikrotik/routeros≥ 7.24, < 7.24.27.24.2
References (8)
EPSS history
Timeline
  • 07 SEP 03:35Z
    EPSS moved — → 0%
    epss
  • 05 SEP 20:00Z
    Kernel memory disclosure and denial of service in MikroTik RouterOS btest service
    cvelistv5