What it is
CVE-2026-67277 is an unauthenticated vulnerability affecting Mikrotik RouterOS. RouterOS accepts a "related" btest connection before the corresponding primary session has completed authentication.
Vulnerability report
Trusted Third Party Report
Confirmed Confidence
In CISA KEV
CVE-2026-67277
RouterOS Denial of Service
Mikrotik / RouterOS · affected before 7.24.2
- Severity
- CVSS 8.8 · High
- Confidence
- Confirmed
- Exploit status
- Trusted Third Party Report
- EPSS
- 1.6%
- First observed
- —
- Last observed
- —
Decision summary
What security teams need to know first
Direct answers before the deeper technical record.
Have exploitation attempts been observed?
Yes. Exploitation attempts have been reported for this vulnerability. Previdian lists it as a known exploited vulnerability. Listed in CISA KEV. Also reported by third-party sources. Confidence is confirmed.
Who is affected?
Mikrotik / RouterOS, including affected before 7.24.2, affected before 7.23.4, and affected before 6.49.21.
What should we do?
Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.
Overview
RouterOS accepts a "related" btest connection before the corresponding primary session has completed authentication
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)
Vendor
Product
Affected
Status
Mikrotik
Affected
RouterOS
Before 7.24.2
Before 7.23.4
Before 6.49.21
Affected
- Published
- 05 Sep 2026
- Exploitation Attempts Reported
- 10 Sep 2026
- Attack vector
- Remote
- Complexity
- Low
- Privileges
- None
- User interaction
- None
Tags
edge
cisa
CVE References
- CVE Record CVE.org · CVE Record https://www.cve.org/CVERecord?id=CVE-2026-67277
- Vendor Advisory — mikrotik.com mikrotik.com · Vendor Advisory https://mikrotik.com/supportsec/september-2026-vulnerability/
- Third-Party Advisory — cert.pl cert.pl · Third-Party Advisory https://cert.pl/en/posts/2026/09/mikrotik-routeros-cve
- Exploit — npratley.net npratley.net · Exploit https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-...
- Technical Description — cert.pl cert.pl · Technical Description https://cert.pl/en/posts/2026/09/vulnerabilities-in-mikrotik-routeros...
- Release Notes — forum.mikrotik.com forum.mikrotik.com · Release Notes https://forum.mikrotik.com/t/6-49-21-long-term-is-released/272802
- Release Notes — forum.mikrotik.com forum.mikrotik.com · Release Notes https://forum.mikrotik.com/t/7-23-4-long-term-is-released/272801
- Release Notes — forum.mikrotik.com forum.mikrotik.com · Release Notes https://forum.mikrotik.com/t/7-24-2-stable-is-released/272800
Exploitation evidence
Evidence of exploitation attempts
Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.
Exploitation Attempts Observed in the Wild
CISA
A trusted third party reported exploitation attempts.
Known exploited vulnerability sources
Per-source evidence links for KEV attestations are available through the Previdian Pro API.
Learn about Pro API access| Source | Added |
|---|---|
| CISA First | 2026-09-10 19:50 UTC |
| CVE | 2026-09-10 20:01 UTC |
Detection
Operational artifacts and observed signals
Make the evidence actionable in scanner, SOC, and edge-control workflows.
Scanner coverage
No scanner integrations recorded yet.
Virtual patch status
No Previdian virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.
Learn about virtual patches →No detection artifacts or sensor request patterns are available for this CVE yet.
Check back as sensor telemetry and scanner integrations are updated.
Risk and context
Severity, weaknesses, and research context
CVSS v4.0
8.8
High
Potential damage if exploited. Separate from whether attackers are using it.
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
1.6%
Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.
Timeline
From disclosure to observed exploitation attempts
-
20:01 UTC
KEV confirmed by CVE
Exploitation attempts reported by an external source
-
19:50 UTC
Added to CISA KEV
Listed in the CISA Known Exploited Vulnerabilities catalog
-
20:00 UTC
CVE published
Vulnerability disclosed publicly
-
11:59 UTC
CVE ID reserved
Identifier reserved by the CNA
Pro API
Automate this intelligence
Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.
- Evidence confidence and provenance
- First-party sensor telemetry
- PoC and scanner references
- Affected versions and enrichment
- Automation-ready JSON delivery
GET /api/v2/pro/kevs/CVE-2026-67277
Sample API response{
"cve_id": "CVE-2026-67277",
"confidence": "Confirmed",
"cvss_score": 8.8,
"cvss_estimated": false,
"epss_score": 0.0156,
"exploit_status": {
"exploited_in_the_wild": true,
"active_exploitation_observed": false
},
"sensor_telemetry": { "attempts": 0, "sensors": 0 }
}