Remote DoS attack against SSH Secure Shell for Windows Servers Vulnerability

2001-03-15T00:00:00
ID SECURITYVULNS:DOC:1395
Type securityvulns
Reporter Securityvulns
Modified 2001-03-15T00:00:00

Description

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                               U.S.S.R labs
                         Buenos Aires, Argentina
                         http://www.ussrback.com

Topic: Remote DoS attack against SSH Secure Shell for Windows Servers Vulnerability USSR Advisory Code: USSR-2001001 Announced: 2001-03-16 Credits: Luciano Martins <luck@ussrback.com> Affects: SSH Secure Shell for Windows Server 2.4 Corrected: SSH Secure Shell for Windows Server 2.5 available soon Vendors Affected: SSH Communications Security Corp http://www.ssh.com/

  1. Discussion

UssrLabs has recently discovered a problem with Windows versions of sshd. The problem lies with adjacent connection handling where the sshd is unable to handle 64 simulataneous connections. As a result the sshd will crash, and no services to the sshd will be accepted.

The problem lies in ssheloop.c where the assertion test fails.

The Event Log displays the following code after 64 connections are spawned:

FATAL ERROR: E:\src\lib\sshutil\ssheloop\win32\ssheloop.c:1597 SshEventLoop (function name unavailable) Assertion failed: ssh_adt_num_objects(ssh_eloop_events) < 64

No doubt, proper error handling techniques have not been implemented for the SshEventLoop which ultimately causes the crash.

This results in a Denial of Service against the service in question.

  1. Vendor Status: Informed, Contacted.

  2. Fix: official fix will be available soon.

Related Links:

Underground Security Systems Research: http://www.ussrback.com

CrunchSp Product: http://www.crunchsp.com

About:

USSR is an emerging security company based in South America. We are devoted to network security research, vulnerability research, and software protection systems. One of the main objectives of USSR is to develop and implement cutting edge security and protection systems that cater to an evolving market.

We believe that the way we implement security solutions can make a difference. CrunchSP is an example, providing a solution to software piracy. Our solutions such as CrunchSP are devoted to protecting your enterprise.

On a daily basis, we research, develop, discover and report vulnerability information. We make this information freely available via public forums such as BugTraq, and our advisory board located at http://www.ussrback.com.

The USSR is a highly skilled, experienced team. Many USSR programmers, as well as programmers of partners and affiliates, are seasoned professionals, with 12 or more years of industry experience. A knowledge base of numerous computer applications as well as many high and low level programming languages makes USSRback a diverse team of experts prepared to serve the needs of any customer.

USSR has assembled some of the world's greatest software developers and security consultants to provide our customers with a wide range of enterprise level services. These services include:

  • Network Penetration Testing
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For more information, please contact us via email at labs@ussrback.com.

Copyright (c) 1999-2000 Underground Security Systems Research. Permission is hereby granted for the redistribution of this alert electronically. It is not to be edited in any way without explicit consent of USSR. If you wish to reprint whole or any part of this alert in any other medium excluding electronic medium, please e-mail labs@ussrback.com for permission.

Disclaimer: The information within this paper may change without notice. We may not be held responsible for the use and/or potential effects of these programs or advisories. Use them and read them at your own risk or not at all. You solely are responsible for this judgment.

Feedback:

If you have any questions, comments, concerns, updates, or suggestions please feel free to send them to:

Underground Security Systems Research mail:labs@ussrback.com http://www.ussrback.com

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