libssh publickey_from_privatekey() function denial of service

Notification Type: IBM Security Protection Advisory
Notification Date: February 14, 2013
Notification Version: 1.0
Name: libssh publickey_from_privatekey() function denial of service
Public disclosure/
In the wild date:
January 22, 2013
CVE: CVE-2013-0176

libssh is vulnerable to a NULL-dereference condition which can lead to a DOS of the server application.

Discoverer: This vulnerability was discovered and researched by Yong Chuan Koh of IBM X-Force.


ISS Coverage

Product Content Version
Network Protection XGS
Proventia Network IDS
Proventia Network IPS
Proventia MFS
Proventia Server (Linux)
RealSecure Network
RealSecure Server Sensor
Virtual Server Protection for VMware
Proventia Desktop
Proventia Server IPS (Windows)
Propagation Techniques ISS Protection Available

Denial of Service

12 Feb 2013

Detailed Description

Business Impact:

Successful attacks will cause vulnerable server applications to become unresponsive, denying service to legitimate users.

*CVSS Base Score: 7.8
  Access Vector: Network
Access Complexity: Low
Authentication: None
Confidentiality Impact: None
Integrity Impact: None
Availability Impact: Complete
Adjusted Temporal Score: 6.8
  Exploitability: High
Remediation Level: Official-Fix
Report Confidence: Confirmed
Affected Products:

See References for details.

Technical Description:

During the "Key Exchange Init" exchange, the server sets up the session by matching the algorithms preferred by the client against what is supported. If there is no match, a variable remains uninitialized. On a subsequent "Diffie-Hellman Key Exchange Init" from client, this is dereferenced and leads to a crash.


Upgrade to the latest version of libssh (0.5.4 or later), available from the libssh Web site. See References.



Revision History

1.0 Initial publication.

* According to the Forum of Incident Response and Security Teams (FIRST), the Common Vulnerability Scoring System (CVSS) is an "industry open standard designed to convey vulnerability severity and help to determine urgency and priority of response." IBM PROVIDES THE CVSS SCORES "AS IS" WITHOUT WARRANTY OF ANY KIND, INCLUDING THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. CUSTOMERS ARE RESPONSIBLE FOR ASSESSING THE IMPACT OF ANY ACTUAL OR POTENTIAL SECURITY VULNERABILITY.
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