Threat Intelligence / CVE / CVE-2026-67277

CVE-2026-67277 — Mikrotik RouterOS

CVSS v4.0 8.8 (High, derived from score) · EPSS 0.4% (higher than 36.5% of all scored CVEs) · Priority 7.9/10 · Published 2026-09-05

As of 2026-09-05, CVE-2026-67277 is a High-severity (band derived from the CVSS v4.0 score, not stated by the CNA) vulnerability in Mikrotik RouterOS, CVSS v4.0 8.8, EPSS 0.4% (36.5th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-67277, most recently “Attackers Hijack MikroTik Routers Through Internet-Exposed SSH Without Authentication (MikroTrick)”.

Last updated: 2026-09-05

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)

The record classifies CVE-2026-67277 under weakness class CWE-306. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 13 days ago.

Severity and exploitation probability

CVSS v4.0 base score
8.8 — High (derived from score)
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 (FIRST)
0.4% probability of exploitation in the next 30 days, higher than 36.5% of all scored CVEs
CISA KEV
Not listed in the CISA Known Exploited Vulnerabilities catalog
Threadlinqs priority
7.9/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
Published
2026-09-05

Is CVE-2026-67277 being exploited?

Weaponised exploit code for CVE-2026-67277 is publicly available. 1 public proof-of-concept repository is tracked for this identifier. It currently carries a trending score of 47 in the Threadlinqs vulnerability feed.

Affected products and versions

How to fix CVE-2026-67277

No vendor patch reference has been recorded for CVE-2026-67277 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

Threat activity tracking CVE-2026-67277

1 tracked threat in the Threadlinqs corpus references CVE-2026-67277, either in the campaign’s CVE list or as an indicator on the campaign record.

Sources

Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories, public proof-of-concept repositories. Last verified by Threadlinqs on . This product uses the NVD API but is not endorsed or certified by the NVD.

Vendor advisory and patch

Exploit and proof of concept

Technical analysis

Third-party advisory

Full detection coverage & IOCs for threats exploiting CVE-2026-67277 are available via the Threadlinqs MCP server (Purple tier). View plans →

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