Vulnerability Note VU#419241

Multiple vendor SFTP logging format string vulnerability

Original Release date: 13 Feb 2006 | Last revised: 15 Feb 2006

Overview

A logging function used by multiple vendors' SFTP servers contains a format string vulnerability, which may allow an authorized remote attacker to execute arbitrary code or cause a denial of service.

Description

SFTP

SFTP (Secure FTP) is a file transfer application that uses SSH for encryption.

The problem

The logging function of several vendors' SFTP servers contains a format string vulnerability.

Vulnerable products include:

  • Reflection for Secure IT UNIX Server version 6.0
  • Reflection for Secure IT Windows Server version 6.0
  • F-Secure SSH Server for Windows version 5.x
  • F-Secure SSH Server for UNIX version 3.x through 5.x

Impact

A remote authenticated attacker may be able to execute arbitrary code with the privilege of the user or cause a denial of service to the SSH server.

Solution

Upgrade or patch


AttachmateWRQ Reflection for Secure IT and F-Secure SSH Server users should install an upgrade, as specified in WRQ Tech Note 1882.


According to the WRQ Tech note, the following workaround may prevent exploitation of the vulnerability:

    On UNIX Servers

       1. Edit the SSH server's sshd2_config file:

             1. Change the line

                subsystem-sftp internal://sftp-server

                to

                subsystem-sftp sftp-server

                Note: This change disallows the use of chroot.

             2. Comment out the SftpSyslogFacility keyword line. Note: The line should begin with two "pound" signs, as in this example:

                ## SftpSyslogFacility LOCAL7

       2. Restart the SSH server to read the changes in the configuration file.

    On Windows Servers
    The only workaround is to disable the sftp subsystem as follows:

       1. Edit the SSH server's sshd2_config file and comment out the subsystem-sftp line. Note: The line should begin with two "pound" signs, as in this example:

                ## subsystem-sftp "fsshsftpd.exe"

       2. Restart the SSH server to read the change in the configuration file.

Systems Affected (Learn More)

VendorStatusDate NotifiedDate Updated
F-Secure CorporationAffected16 Jan 200615 Feb 2006
WRQ, Inc.Affected-15 Feb 2006
BitviseNot Affected16 Jan 200617 Jan 2006
InterSoft InternationalNot Affected16 Jan 200618 Jan 2006
MacSSHNot Affected16 Jan 200616 Jan 2006
OSSHNot Affected16 Jan 200616 Jan 2006
PuTTYNot Affected16 Jan 200616 Jan 2006
VanDyke SoftwareNot Affected16 Jan 200617 Jan 2006
FiSSHUnknown16 Jan 200616 Jan 2006
lshUnknown16 Jan 200616 Jan 2006
OpenSSHUnknown16 Jan 200616 Jan 2006
Pragma SystemsUnknown16 Jan 200616 Jan 2006
TTSSHUnknown16 Jan 200616 Jan 2006
WinSCPUnknown16 Jan 200616 Jan 2006
If you are a vendor and your product is affected, let us know.

CVSS Metrics (Learn More)

Group Score Vector
Base N/A N/A
Temporal N/A N/A
Environmental N/A N/A

References

Credit

Thanks to WRQ for reporting this vulnerability.

This document was written by Will Dormann.

Other Information

  • CVE IDs: Unknown
  • Date Public: 13 Feb 2006
  • Date First Published: 13 Feb 2006
  • Date Last Updated: 15 Feb 2006
  • Severity Metric: 3.37
  • Document Revision: 9

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