CVE-2004-1897

Vulnerability

A denial of service vulnerability exists in the administration interface of Monit versions 1.4 through 4.2 (and 4.3 Beta 2 and prior) [2]. When processing a Basic authentication request without a password, Monit decrements a pointer returned by strchr() without a NULL check, leading to an out-of-bounds read and segmentation fault [2]. The vulnerability is exploitable only when the HTTP/HTTPS administration interface is enabled [2].

Exploitation

An attacker can exploit this vulnerability by sending a crafted HTTP request with Basic authorization but omitting the password field [2]. No authentication is required; the request can be generated using a simple web browser [2]. The exact sequence involves base64-decoding the credentials, where the absence of a password causes the pointer manipulation and subsequent crash [2].

Impact

Successful exploitation causes Monit to terminate with a segmentation fault, resulting in a denial of service [2]. The vulnerability does not allow privilege escalation or data disclosure; the impact is solely on availability of the monitoring service [2].

Mitigation

The vulnerability is fixed in Monit versions later than 4.2 (e.g., 4.3 and above) [2]. Users should upgrade to a patched version. As a workaround, disable the administration interface if not required, or restrict network access to trusted hosts [2].