Clam Antivirus DoS vulnerability

1. Gentoo Linux Security Advisory

Advisory Reference	GLSA 200402-07 / clamav
Release Date	February 17, 2004
Latest Revision	February 17, 2004: 01
Impact	normal
Exploitable	remote

Package	Vulnerable versions	Unaffected versions	Architecture(s)
app-antivirus/clamav	< 0.67	>= 0.67	All supported architectures

Related bugreports: #41248

Synopsis

Oliver Eikemeier has reported a vulnerability in Clam AV, which can be exploited by a malformed uuencoded message causing a denial of service for programs that rely on the clamav daemon, such as SMTP daemons.

2. Impact Information

Background

Clam AntiVirus is a GPLed anti-virus toolkit, designed for integration with mail servers to perform attachment scanning. Clam AV also provides a command line scanner and a tool for fetching updates of the virus database.

Description

Oliver Eikemeier of Fillmore Labs discovered the overflow in Clam AV 0.65 when it handled malformed UUEncoded messages, causing the daemon to shut down.

The problem originated in libclamav which calculates the line length of an uuencoded message by taking the ASCII value of the first character minus 64 while doing an assertion if the length is not in the allowed range, effectively terminating the calling program as clamav would not be available.

Impact

A malformed message would cause a denial of service, and depending on the server configuration this may impact other daemons relying on Clam AV in a fatal manner.

3. Resolution Information

Workaround

There is no immediate workaround, a software upgrade is required.

Resolution

All users are urged to upgrade their Clam AV installations to Clam AV 0.67:

Code Listing 3.1: Resolution

# emerge sync
# emerge -pv ">=app-antivirus/clamav-0.6.7"
# emerge ">=app-antivirus/clamav-0.6.7"

Page updated February 17, 2004

Summary: This is a Gentoo Linux Security Advisory

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