MikroTik RouterOS <7.24 SMB1 Heap Corruption via uniPwdLen Underflow
CVE-2026-89028 Published on September 16, 2026
MikroTik RouterOS < 7.24 Heap Corruption via SMB1 SessionSetupAndX
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 Analysis
CVE-2026-89028 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity and availability.
Weakness Types
Heap-based Buffer Overflow
A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().
What is an Integer underflow Vulnerability?
The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result. This can happen in signed and unsigned cases.
CVE-2026-89028 has been classified to as an Integer underflow vulnerability or weakness.
Products Associated with CVE-2026-89028
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Affected Versions
MikroTik RouterOS:- Before and including 6.49.18 is affected.
- Version 7.0.0, <= 7.11.2 is affected.
- Version 7.24.0 is unaffected.