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CVE-2026-67277

HIGH 8.8 KNOWN EXPLOITED ALL-YEARS

Published 2026-09-05 · Last modified 2026-09-11 · CERT-PL · NVD: Analyzed

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)

ACTIVELY EXPLOITED

Confirmed exploited in the wild — in CISA KEV since 2026-09-10. Patch or mitigate now.

Exploitation likelihood

1.6%chance of exploitation in 30 days · 75th percentile

● In CISA KEV (2026-09-10)○ Catalogued PoC◆ SSVC: exploitation active, automatable yes

Impact if exploited

8.8CVSS 4.0 · HIGH · CNA

  • ConfidentialityLow
  • IntegrityNone
  • AvailabilityHigh

What an attacker needs

  • ✓Access: Reachable over the network — no local access needed
  • ✓Privileges: No account or privileges required
  • ✓User interaction: No user interaction needed
  • ✓Complexity: No special conditions — reliably repeatable
  • ✓Requirements: No special attack requirements

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept

No public PoC is currently catalogued.

Search for new PoCs

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Tracked sources are checked weekly for the full archive, including PoCs published after the original disclosure. A later release appears after a tracked source lists it and a refresh succeeds.

Data snapshot:

Affected

Vendors Mikrotik

Products Routeros

Weakness (CWE)

  • CWE-306: Missing authentication for critical function

CVSS vector

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

References and research data (JSON)

Additional exploitation reports

Source-specific reports, separate from CISA KEV. Repeated observations from one source are not independent confirmations.

  • ENISA EU KEV · 2026-09-05EUVD · EUVD-2026-72025
  • VulnCheck KEV · 2026-09-05T00:00:00Z

    Source guidance: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

    Source ransomware assessment: Unknown

    VulnCheck KEV · CVE-2026-67277 · Updated 2026-09-05T00:00:00Z
  • VulnCheck KEV · 2026-09-05T00:00:00ZVulnCheck KEV · CVE-2026-67277
  • VulnCheck KEV · 2026-09-10T00:00:00ZVulnCheck KEV · CVE-2026-67277

Known Affected Software Configurations

VendorProductVersion range
MikrotikRouteros≥ 6.0 and < 6.49.21
MikrotikRouteros≥ 7.0 and < 7.23.4
MikrotikRouteros≥ 7.24 and < 7.24.2

All CVSS metrics

  • HIGH 8.8 v4.0 · CNA Primary
    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
  • HIGH 8.8 v4.0 · NVD Secondary
    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
  • HIGH 8.2 v3.1 · NVD Primary
    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H

References

Exploit-tagged references (not proof of a PoC)

Patches & mitigations

Advisories

Technical & other

Sources: NVD · CVE.org · All sources and attribution · EPSS