Quick answers
- Is CVE-2026-39042 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-39042 being exploited in the wild.
- How severe is CVE-2026-39042?
- Informational severity, with a CVSS score of 0, published 13 July 2026.
- Which products and versions are affected?
- MikroTik RouterOS 7.21.x before 7.21.4, 7.22.x before 7.22.2.
- Is there a fix for CVE-2026-39042?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-39042 attacked?
- It is attacked over the network, in an operating system.
- Am I affected by CVE-2026-39042?
- Check whether you run MikroTik RouterOS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
An integer overflow vulnerability exists in the core IPC library (libumsg.so) of MikroTik RouterOS. Specifically, the unflatten() function fails to properly validate input, allowing a remote attacker to trigger a denial of service (DoS) condition. The issue affects RouterOS versions 7.21.x (prior to 7.21.4) and 7.22.x (prior to 7.22.2). Exploitation occurs via the network and results in a crash of the affected service. Patches are available in RouterOS versions 7.21.4 and 7.22.2.
Affected products
- MikroTik RouterOS 7.21.x before 7.21.4, 7.22.x before 7.22.2
Timeline
- 2026-07-13: advisory
- 2026-07-13: disclosed