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.
CVE-2026-39042
HIGHPre-NVD 7.5Trending — 4 sources updated this week
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.5Exploit: NoneExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 7.5
- EG Score
- 0.0(none)
- EPSS
- 33.1%
- KEV
- Not listed
Published
July 13, 2026
Last Modified
July 15, 2026
Advisory Details (2)
Auto-updated Jul 15, 2026No patch confirmed yet.
generic
Patrik Žák — Ethical Hacker & Red Teamer
https://zakpatrik.cz/blog/finding-an-integer-overflow-in-mikrotik-routeros-core-ipc-libraryVendor Advisories for CVE-2026-39042(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 7× in last 7d / 7× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-15 16:57 UTCEPSS rescore
- 2026-07-15 16:57 UTCEPSS rescore
- 2026-07-15 02:00 UTCEPSS rescore
- 2026-07-14 16:40 UTCMITRE cvelistV5CVSS v3 → 7.5 · severity → HIGH
- 2026-07-13 22:28 UTCNVD update
- 2026-07-13 22:03 UTCEG score recompute
- 2026-07-13 22:02 UTCMITRE cvelistV5first tracked
Related CVEs(same CWE)
Same CWE
10 shownCWE-190
- CVE-2009-0947EG 9.8CRITICAL
- CVE-2013-2729EG 9.8 KEVEPSS 99%CRITICAL
- CVE-2005-1141EG 9.8CRITICAL
- CVE-2005-0102EG 9.8CRITICAL
- CVE-2002-0391EG 9.8EPSS 99%CRITICAL
- CVE-2002-0639EG 9.8EPSS 97%CRITICAL
- CVE-2013-3486EG 9.6CRITICAL
- CVE-2013-2596NVD 7.8EG 9.0 KEVHIGH
- CVE-2012-5054NVD 8.8EG 9.0 KEVEPSS 97%HIGH
- CVE-2011-1823NVD 7.8EG 9.0 KEVEPSS 99%HIGH
Frequently asked(5)
What is CVE-2026-39042?
CVE-2026-39042 is a high vulnerability published on July 13, 2026. 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.
When was CVE-2026-39042 disclosed?
CVE-2026-39042 was first published in the National Vulnerability Database on July 13, 2026, with the most recent update on July 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-39042 actively exploited?
CVE-2026-39042 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 33.1% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-39042?
CVE-2026-39042 has a CVSS v3.1 base score of 7.5 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 0.0.
How do I remediate CVE-2026-39042?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-39042, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2026-39042
Is Your Infrastructure Affected by CVE-2026-39042?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.