vulnerability note CVE-2012-3482

fetchmail: denial of service via NTLM

Synthesis of the vulnerability

An attacker can invite the victim to use fetchmail to connect to a server using an invalid NTLM authentication, in order to stop fetchmail.
Impacted products: Fedora, MBS, MES, Mandriva Linux, Solaris, Unix (platform).
Severity: 1/4.
Creation date: 14/08/2012.
Identifiers: BID-54987, CVE-2012-3482, FEDORA-2012-14451, FEDORA-2012-14462, fetchmail-SA-2012-02, MDVSA-2012:149, MDVSA-2013:037, VIGILANCE-VUL-11844.

Description of the vulnerability

The fetchmail program downloads emails from a POP or an IMAP server.

This server can use an NTLM authentication. In this case, the ntlm_helper() function of the ntlmsubr.c file decodes the challenge encoded in base64. However, if the server returned malformed data, fetchmail does not detect the base64 decoding error, and then reads at an unallocated memory address.

An attacker can therefore invite the victim to use fetchmail to connect to a server using an invalid NTLM authentication, in order to stop fetchmail.
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