CVE-2026-67277

HIGH CISA KEV
Published Sep 5, 2026 Modified Sep 11, 2026 CWE-306

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)

Is your site exposed to CVE-2026-67277?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

8.2
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H

EPSS — Exploit Prediction

0.0087
Probability of exploitation
0.57%
Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

CISA Known Exploited Vulnerability

This vulnerability is actively exploited in the wild.

Added: Sep 10, 2026 Remediation due: Sep 13, 2026

Weakness Type (CWE)

CWE-306 Missing Authentication

Affected Products

Vendor Product
mikrotik routeros
mikrotik routeros
mikrotik routeros

References

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) It has a CVSS v3.1 base score of 8.2 (HIGH). This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog, indicating active exploitation in the wild.
How severe is CVE-2026-67277? +
CVE-2026-67277 has a CVSS v3.1 score of 8.2 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0087, placing it in the 1th percentile for exploitation probability.
What products are affected by CVE-2026-67277? +
CVE-2026-67277 affects products from mikrotik, specifically: routeros. Check the affected products table above for specific version ranges.
How do I check if I'm vulnerable to CVE-2026-67277? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-6369

An improper access control vulnerability in the canonical-livepatch snap client prior to version 10.15.0 allows a local unprivileged user to …
CVE-2026-9152

A missing authentication vulnerability exists in the Altium 365 SearchService. A legacy SOAP endpoint exposes search index operations without requiring …
CVE-2026-5749

Inadequate access control in the registration process in Fullstep V5, which could allow unauthenticated users to obtain a valid JWT …
CVE-2026-6376

A weakness in SpiceJet’s public booking retrieval page permits full passenger booking details to be accessed using only a PNR …
CVE-2024-45483

A Missing Authentication for Critical Function vulnerability in the GRUB configuration used B&R APROL <4.4-01 may allow an unauthenticated physical …
CVE-2024-54013

Penetration Testing engineers at Amazon have identified a security flaw related to request handling in the web server component that …

Don't wait for an exploit

Scan your website for vulnerabilities like CVE-2026-67277 — free, no signup required.