CVSS2
Attack Vector
NETWORK
Attack Complexity
LOW
Authentication
NONE
Confidentiality Impact
PARTIAL
Integrity Impact
NONE
Availability Impact
NONE
AV:N/AC:L/Au:N/C:P/I:N/A:N
EPSS
Percentile
98.7%
A vulnerability in the handling of the NEW-ENVIRON command allows a malicious telnet server to gain information from a client’s environment variables.
The Telnet network protocol is described in RFC854 and RFC855 as a general, bi-directional communications facility. The Telnet protocol is commonly used for command-line login sessions between Internet hosts.
The vulnerability is in the NEW-ENVIRON sub-command that is the mechanism to used for passing environment information between a telnet client and server. Use of this mechanism enables a telnet user to propagate configuration information to a remote host when connecting. Please see RFC1572 for more information. As specified in section 3 of RFC1572 the expected default behavior should be “that there will not be any exchange of environment information”.
In order to exploit this vulnerability, a malicious server can send a connected client the following telnet command:
SB NEW-ENVIRON SEND ENV_USERVAR <name of environment variable> SE
Vulnerable telnet clients will send the value of the referenced environment variable. Environment variables may contain a variety of the information such as local username, executable file search paths, locations of sensitive data, and other potentially sensitive information about the client computer.
Please note telnet functionality has been embedded in many applications and not just underlying operating systems distributions.
The iDefense Security Advisory contains additional information about affected and unaffected vendors.
An attacker may be able to gather information about remote systems and users who connect to attackers malicious telnet server. An attacker would have to trick a victim into initiating a telnet connection using a vulnerable client. This may be accomplished with an HTML rendered email or web page, using the TELNET:// URI handler, however further user interaction may be required.
Apply an update from your vendor
Patches, updates, and fixes should be available from multiple vendors.
Workarounds
Disable access to telnet, limit the use of telnet to trusted sites and/or encourage the use more secure remote connection clients.
On Unix systems it might be viable to remove execute permission from telnet and other binaries that perform telnet.
On Windows systems changing or removing the registry key entry: HKEY_CLASSES_ROOT\telnet\shell\open\command
should reduce the likelihood of successful automatic exploitation attempts such as those using telnet URLs.
Note these workarounds do not address the underlying vulnerability.
800829
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Updated: June 14, 2005
Affected
We have not received a statement from the vendor.
The vendor has not provided us with any further information regarding this vulnerability.
Microsoft has issued patches in relation to this vulnerability, for more information see Microsoft Security Bulletin MS05-033:
<http://www.microsoft.com/technet/security/bulletin/MS05-033.mspx>
If you have feedback, comments, or additional information about this vulnerability, please send us [email](<mailto:[email protected]?Subject=VU%23800829 Feedback>).
Updated: July 28, 2005
Affected
Vendor Statement: Red Hat, Inc
Updates are available for Red Hat Enterprise Linux 2.1, 3 and 4 to correct
this issue. New telnet and Kerberos packages along with our advisory are
available at the URL below and by using the Red Hat Network ‘up2date’ tool.
<http://rhn.redhat.com/errata/CAN-2005-0488.html>
The vendor has not provided us with any further information regarding this vulnerability.
Red Hat Inc. has released a security update in relation to this issue:
<https://rhn.redhat.com/errata/RHSA-2005-504.html>
If you have feedback, comments, or additional information about this vulnerability, please send us [email](<mailto:[email protected]?Subject=VU%23800829 Feedback>).
Updated: June 14, 2005
Affected
We have not received a statement from the vendor.
The vendor has not provided us with any further information regarding this vulnerability.
Sun Microsystems have issued two Sun(sm) Alert Notifications in relation to this vulnerability including workaround and patch information. For more information please see:
<http://sunsolve.sun.com/search/document.do?assetkey=1-26-57755-1>
<http://sunsolve.sun.com/search/document.do?assetkey=1-26-57761-1>
If you have feedback, comments, or additional information about this vulnerability, please send us [email](<mailto:[email protected]?Subject=VU%23800829 Feedback>).
Group | Score | Vector |
---|---|---|
Base | ||
Temporal | ||
Environmental |
Gaël Delalleau is credited with this discovery. Thank you to iDefense for coordinating the release of information about this issue.
This document was written by Robert Mead based on information in the iDEFENSE Security Advisory
CVE IDs: | CVE-2005-0488 |
---|---|
Severity Metric: | 0.17 Date Public: |