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Vulnerability of Sendmail: buffer overflow via X-Testing

Synthesis of the vulnerability

On old Sendmail versions, an attacker can use a long X-Testing header in order to generate a denial of service and possibly to execute code.
Severity of this computer vulnerability: 2/4.
Number of vulnerabilities in this bulletin: 2.
Creation date: 07/05/2009.
Références of this announce: BID-34944, BID-34949, CVE-2009-1490, CVE-2009-1491, VIGILANCE-VUL-8698.

Description of the vulnerability

A vulnerability was announced in 2009, about Sendmail versions available in 2004.

An email is composed of headers and a body. Headers can contain extensions starting by "X-".

When the first header is a long extension, Sendmail tries to split it on several lines. However, two cases can occur:
 - a computation error generates a buffer overflow
 - the end of the header can be inserted in the message body

This vulnerability can therefore lead:
 - to a denial of service or to code execution
 - to a malformed email which can bypass an antivirus.
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This security threat impacts software or systems such as Sendmail.

Our Vigil@nce team determined that the severity of this computer weakness note is medium.

The trust level is of type confirmed by the editor, with an origin of internet client.

This bulletin is about 2 vulnerabilities.

An attacker with a expert ability can exploit this computer threat alert.

Solutions for this threat

Sendmail: version 8.13.2.
Version 8.13.2 is corrected:
  http://www.sendmail.org/
Note: this version was published in 2004, but details about a vulnerability it corrected were only published in 2009.
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