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CVE-2026-67277

HIGHCVSS 4.0 · 8.8 · cvd@cert.pl

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

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)

CISA KEV: known exploited

Added: 2026-09-10 · Due: 2026-09-13

Known ransomware use: Unknown

EPSS: 1.56% · Percentile: 75.1%

As of 2026-10-27

EPSS estimates exploitation probability over the next 30 days. KEV due dates apply to US federal civilian agencies. Confirm your affected versions in vendor advisories.

CWE: CWE-306 · Published: 2026-09-05T20:17:18.120 · Modified: 2026-09-11T12:52:29.533

Sources: NIST NVD, CISA KEV, FIRST EPSS. NVD and EPSS cached up to 6 hours; KEV up to 12 hours.

All CVSS assessments
  • CVSS 4.0: 8.8 (HIGH) · cvd@cert.pl
    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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
  • CVSS 3.1: 8.2 (HIGH) · NIST NVD
    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H

References and fixes