# CVE-2026-67277: MikroTik RouterOS Missing Authentication for Critical Function

> Unauthenticated attackers can leak kernel memory and crash the RouterOS kernel via the btest service.

- **Severity:** High 8.8 (`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`)
- **Exploited in the wild:** Yes, since 10 Sep 2026 (CISA KEV)
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 5 Sep 2026
- **Updated:** 11 Sep 2026
- **Also known as:** GHSA-6q2x-6fhj-r3w8

## What is CVE-2026-67277?

CVE-2026-67277 is a high-severity vulnerability in Mikrotik Routeros, published on 5 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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)

Weakness: CWE-306 (Missing Authentication for Critical Functionality)

## Which versions are affected by CVE-2026-67277?

It affects 1 product.


Products: Mikrotik Routeros.

## How do I fix CVE-2026-67277?

No fix has been published for CVE-2026-67277 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 13 Sep 2026.

## Is CVE-2026-67277 being exploited?

Yes. Attackers have exploited CVE-2026-67277 in the wild since at least 10 Sep 2026.

## Other vulnerabilities in Mikrotik Routeros

- [CVE-2018-7445](https://insights.sbomify.com/CVE-2018-7445/): MikroTik RouterOS Stack-Based Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2026-86060](https://insights.sbomify.com/CVE-2026-86060/): MikroTik RouterOS Improper Neutralization of Argument Delimiters in a Command (critical 9.2, exploited in the wild)
- [CVE-2018-14847](https://insights.sbomify.com/CVE-2018-14847/): MikroTik Router OS Directory Traversal (critical 9.1, exploited in the wild)
- [CVE-2026-67279](https://insights.sbomify.com/CVE-2026-67279/): Mikrotik RouterOS Improper Enforcement of Behavioral Workflow (medium 6.9, exploited in the wild)
- [CVE-2017-20149](https://insights.sbomify.com/CVE-2017-20149/): Memory corruption in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-67277 and fix it if it is affected.

What it is: CVE-2026-67277 is a high-severity vulnerability in Mikrotik Routeros, published on 5 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2026-67277 in the wild since at least 10 Sep 2026.

Affected product: Mikrotik Routeros. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-67277/ (Markdown: https://insights.sbomify.com/CVE-2026-67277/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-67277
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-67277
- OSV: https://osv.dev/vulnerability/CVE-2026-67277

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-67277/
Summaries are generated and may contain mistakes; the official description above is the record.