CVE-2026-39042: An issue in MikroTIk (SIA Mikrotikls, Latvia) RouterOS 7.21.x before v.7.21.4 and 7.22.x before v.7.22.2 allows a remote attacker to cause a denial of service via the unflatten() f
An issue in MikroTIk (SIA Mikrotikls, Latvia) RouterOS 7.21.x before v.7.21.4 and 7.22.x before v.7.22.2 allows a remote attacker to cause a denial of service via the unflatten() function in libumsg.so.
Details
Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-39042
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Low exploitation riskCVE-2026-390420.41% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 34% of all scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-39042 | coverage & exploitation status | NVD · CVE.org |
Recent advisories for MikroTIk
A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.
- mediumCVE-2026-14227: An API session‑management flaw in products with the MikroTik RouterOS API enabled are vulnerab…nvd · 2026-07-30
- criticalMikroTik RouterOScisa · 2026-07-30
- highCVE-2026-16347: MikroTik RouterOS contains a weakness in its API authentication handling that lacks effective …nvd · 2026-07-28
- criticalMikroTik RouterOS and Cloud Hosted Routercisa · 2026-07-28
- criticalexploitedCVE-2018-7445: MikroTik RouterOS Stack-Based Buffer Overflow Vulnerabilitycisa-kev · 2022-09-08
- criticalexploitedCVE-2018-14847: MikroTik Router OS Directory Traversal Vulnerabilitycisa-kev · 2021-12-01
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