Title: Exim Format String Vulnerability
Severity: MODERATE
Description:
Exim is a free, open-source Mail Transfer Agent for Unix systems.
Exim is vulnerable to a locally exploitable format string attack which may compromise root access. The vulnerability exists only when the 'syntax checking' mode is turned on, which it is not by default.
When checking the argument of the 'From:' field in an email message, the hostname component of the argument (email address) is passed to a printf function as part of the format string. As a result, any format specifiers embedded within it are interpreted and acted upon. An attacker can use this behaviour to overwrite arbitrary locations in memory by using special format specifiers.
An attacker may be able to execute arbitrary code by corrupting critical values like function return addresses or PLT entries.
On many systems, 'exim' is installed setuid root. Exploitation of this vulnerability may lead to an elevation of privileges for the attacker.
Affected Products:
- Debian Linux 2.2.0 68k
- Debian Linux 2.2.0 IA-32
- Debian Linux 2.2.0 alpha
- Debian Linux 2.2.0 arm
- Debian Linux 2.2.0 powerpc
- Debian Linux 2.2.0 sparc
- University of Cambridge Exim 3.11.0
- University of Cambridge Exim 3.12.0
- University of Cambridge Exim 3.13.0
- University of Cambridge Exim 3.14.0
- University of Cambridge Exim 3.15.0
- University of Cambridge Exim 3.16.0
- University of Cambridge Exim 3.17.0
- University of Cambridge Exim 3.18.0
- University of Cambridge Exim 3.19.0
- University of Cambridge Exim 3.20.0
- University of Cambridge Exim 3.21.0
- University of Cambridge Exim 3.22.0
References:
- Exim: Exim Homepage
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