FTP transfers of files smaller than 1KB fail and result in empty files on destination server

Product: Other
Version: R81.10 (EOS), R81.20
Last Modified: 2026-07-23

Symptoms

• Files smaller than 1KB transferred via FTP are received as empty files (0KB).
• FTP clients such as FileZilla display errors like " File transfer aborted by user for small files".
• The FTP server responds with " 150 Ok to send data", but the resulting file on the destination is empty.
• Debug logs show ADVP errors with messages such as " allowed writing size: 0 bytes" for small files.

Cause

The Stateful Inspection engine incorrectly sets a variable controlling the transfer buffer size to 0 when the file size is smaller than 1024 bytes (the default value).

The conditional statement in the code blocks the transfer of small files. Larger files are unaffected because their longer transfer duration allows proper connection setup before the buffer size is evaluated.

Solution

This problem was fixed. The fix is included in:

• Jumbo Hotfix Accumulator for R82.10 starting from Take 36
• Jumbo Hotfix Accumulator for R82 starting from Take 118
• Jumbo Hotfix Accumulator for R81.20 starting from Take 158

If you choose not to upgrade, Check Point can supply a Hotfix. Contact Check Point Support to get a Hotfix for this issue.

A Support Engineer will make sure the Hotfix is compatible with your environment before providing the Hotfix.

For faster resolution and verification, please collect CPinfo files from the Security Management Server and Security Gateways involved in the case.

Hotfix installation instructions:

Refer to sk168597 - How to install a Hotfix.

NOTE

This solution has been verified for the specific scenario, described by the combination of Product, Version and Symptoms. It may not work in other scenarios.

Article Properties

Access Level: General
Status: Approved by TAC
Date Created: 2025-10-20
Last Modified: 2026-07-23