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ExploitedIn CISA KEVFix available

CVE-2026-67277

Exploitation confirmed. First attested on 2026-09-05 by CISA-ADP, CISA KEV, GCVE · enisa-cnw-kev, GCVE · previdian.

  • Published2026-09-05
  • Fixed in7.24.2 · 7.23.4 · 6.49.21
  • WeaknessCWE-306

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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)

Timeline

dates in UTC
  1. 2026-09-05Listed as exploited by GCVEGCVE
  2. 2026-09-05Exploitation first reportedGCVE
  3. 2026-09-0520:17CVE publishedNVD
  4. 2026-09-10Added to the CISA KEV catalogCISA KEV
  5. 2026-09-1019:48SSVC exploitation set to activeCISA-ADP

Observed activity

isMalicious corpus · updated 2026-10-27 09:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-67277?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-67277?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Mikrotik routeros
BranchAffectedFixed in
7.24≥ 7.24, < 7.24.27.24.2
7.x≥ 7.0, < 7.23.47.23.4
6.x≥ 6.0, < 6.49.216.49.21

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

  1. Update Mikrotik routeros to 7.24.2 · 7.23.4 · 6.49.21
  2. CISA’s required action: 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.due 2026-09-13

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

CISA Known Exploited Vulnerability

Date Added
2026-09-10
Patch Due Date
2026-09-13
Ransomware Use
Unknown
Required Action
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.

Sources

  • CISA KEVKEV entry2026-09-10
  • GCVEexploitation2026-09-05
  • CISA-ADPSSVC decisionactive2026-09-10
  • OpenCVESSVC decisionactive—
  • CNACVSS 4.08.8read 2026-10-23
  • NVDCVSS 3.18.2read 2026-10-23
  • CNAweakness (CWE)CWE-306read 2026-10-23
  • FIRST EPSSEPSS score1.6 %2026-10-26

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
CVSS 4.0 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/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
Published
2026-09-05
Last Modified
2026-09-11
NVD status
Analyzed

Frequently asked questions

What is CVE-2026-67277?

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)

Is CVE-2026-67277 actively exploited?

Yes. CVE-2026-67277 is on the CISA Known Exploited Vulnerabilities (KEV) catalog, meaning it has been confirmed as actively exploited in the wild. CISA requires federal agencies to patch by 2026-09-13.

What is the CVSS score for CVE-2026-67277?

CVE-2026-67277 has a CVSS v3 base score of 8.2 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H.

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