CVE-2026-67277 - RouterOS accepts a "related" btest connection before the corresponding primary session has completed authentication. An
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)
CRITICAL
CISA KEV
ACTIVELY EXPLOITED
Severity & confidence
Source severityinformational
Platform severitycritical
Confidenceconfirmed
Exploitationactively exploited
CVSS-
Affected
ProductsRouterOS
Reporting sources (3)
NIST NVD - National Vulnerability Database
CISA - Known Exploited Vulnerabilities
CISA - Cybersecurity Advisories
🎯 Why should I care?
- On the CISA Known Exploited Vulnerabilities list.
- Credible sources report active exploitation in the wild.
Timeline & provenance
Published2026-09-05T20:17:18
Last updated2026-10-21T04:58:06
Ingested2026-09-07T15:27:26
FreshnessNEAR-REAL-TIME
Threat typevulnerability
Recommended action
No recommended action published with this item - review the original source.
Next steps
- Identify affected systems in your environment.
- Apply the vendor patch or mitigation guidance.
- Review logs for indicators described in the advisory.
- Follow the affected vendor/product to track updates.
Confidence explanation
This object is reported by 3 independent sources.
Source type: standards · Original: NIST NVD - National Vulnerability Database
