Heap corruption via SMB1 password-length underflow
Published Sep 16, 2026 · Updated Sep 16, 2026
Heap corruption in MikroTik RouterOS allows remote attackers to corrupt SMB heap memory through a crafted SMB1 session request. The SessionSetupAndX handler subtracts from an attacker-controlled uniPwdLen value without preventing integer underflow, then uses the result as a copy length for a smaller heap buffer. The SMB1 service must be reachable; the established consequence is adjacent heap corruption, with no public evidence establishing code execution.
Summary
What happened
Heap corruption in MikroTik RouterOS allows remote attackers to corrupt SMB heap memory through a crafted SMB1 session request. The SessionSetupAndX handler subtracts from an attacker-controlled uniPwdLen value without preventing integer underflow, then uses the result as a copy length for a smaller heap buffer. The SMB1 service must be reachable; the established consequence is adjacent heap corruption, with no public evidence establishing code execution.
The record
- CVE
- CVE-2026-89028
- Published
- Sep 16, 2026
- Updated
- Sep 16, 2026
- Vendor
- MikroTik
- Product
- RouterOS
- Classifications
- T1210
- Attack vector
- network
- Privileges
- Unavailable
Timeline
How it unfolded
- Sep 16, 2026CVE publishedPublication date reported by the CVE source.
- Sep 16, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=0 <=6.49.18
- Affected versionversion=7.0.0 <=7.11.2
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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