Buffer overflow in Mikrotik Routeros
CVE-2026-89028
MikroTik RouterOS before 7.24 contains a heap memory corruption vulnerability in the userspace SMB daemon that allows remote attackers to corrupt adjacent heap memory by supplying a crafted uniPwdLen value in the SMB1 SessionSetupAndX handler. An attacker can send a malformed SMB1 request with a uniPwdLen field that triggers an integer underflow, causing the resulting value to be used as the copy length in a memory copy operation into a smaller heap buffer, corrupting adjacent heap memory.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.006 (47.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 48th percentile — 47.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: 0.000
Affected products
Weakness classification (CWE)
References
- forum.mikrotik.com/t/7-24-stable-is-released/272381 (vendor-advisory, patch)
- www.vulncheck.com/advisories/mikrotik-routeros-heap-corruption-via-smb1-session… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-89028?
- CVE-2026-89028 is a high-severity vulnerability in Mikrotik Routeros, classified under Heap-based Buffer Overflow. CVSS score: 7.5/10. Published 2026-09-16.
- How severe is CVE-2026-89028?
- High severity. CVSS v3 base score is 7.5 out of 10.