Unauthenticated memory corruption via off-by-one length check
Published Aug 5, 2026 · Updated Aug 5, 2026
Out-of-bounds write in FreeModbus LINUXTCP allows remote attackers to corrupt memory with a crafted Modbus TCP packet. xMBPortTCPPool() accepts a 263-byte remainder because its limit check uses greater-than instead of greater-than-or-equal, then recv() writes from offset 7 into a 263-byte static buffer. One unauthenticated packet with an MBAP Length of 264 overwrites seven bytes, including adjacent parser state, and can alter or interrupt the Modbus service.
Summary
What happened
Out-of-bounds write in FreeModbus LINUXTCP allows remote attackers to corrupt memory with a crafted Modbus TCP packet. xMBPortTCPPool() accepts a 263-byte remainder because its limit check uses greater-than instead of greater-than-or-equal, then recv() writes from offset 7 into a 263-byte static buffer. One unauthenticated packet with an MBAP Length of 264 overwrites seven bytes, including adjacent parser state, and can alter or interrupt the Modbus service.
The record
- CVE
- CVE-2026-71263
- Published
- Aug 5, 2026
- Updated
- Aug 5, 2026
- Vendor
- SILA Embedded Solutions GmbH
- Product
- FreeModbus
- Classifications
- CWE-787, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 5, 2026CVE publishedPublication date reported by the CVE source.
- Aug 5, 2026Record updatedLatest update available in the CVE record.
Exploitability
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- Affected versionversion=0 <=*
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What is affected?
Published CVSS scores
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Attacks
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Technologies
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Your stack
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