Title: SpamAssassin BSMTP Mode Buffer Overflow Vulnerability
Severity: HIGH
Description:
SpamAssassin is a mail filter to identify and process spam. It is available for Linux and Unix variant operating systems.
A buffer overflow vulnerability has been reported for SpamAssassin. The vulnerability exists when SpamAssassin has been configured for use with BSMTP (Batch Simple Mail Transfer Protocol) processing.
SpamAssassin uses the program spamc to process mail. 'spamc' is the client program that feeds data to the spamd service that processes email. BSMTP processing is enabled by executing spamc with the '-B' option.
The vulnerability occurs when SpamAssassin is escaping '.' characters when processing email headers. Due to insufficient bounds checking performed by the filter, it is possible for a remote attacker to trigger the buffer overflow condition.
An attacker can exploit this vulnerability by composing a malicious email with specific headers. This will cause the buffer overflow condition in the program, spamc. This may result in malicious attacker-supplied code being executed with the privileges of the spamc process.
It should be noted that this issue allows an attacker to write the value of the '.' character to the LSB of the value stored above the affected buffer. Under some circumstances this may be the function's saved frame pointer but the exploitability of this issue is highly volatile.
This vulnerability was reported to affect SpamAssassin 2.40 to 2.43.
Affected Products:
- Gentoo Linux 1.4.0 _rc1
- Gentoo Linux 1.4.0 _rc2
- SpamAssassin SpamAssassin 2.40.0
- SpamAssassin SpamAssassin 2.41.00
- SpamAssassin SpamAssassin 2.42.00
- SpamAssassin SpamAssassin 2.43.00
References:
- SpamAssassin: SpamAssassin Home Page
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