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Multivendor Vulnerability Alert
Linux/Unix: ClamAV PE File Rebuild Buffer Overflow Vulnerability
ClamAV versions 0.88.4 and prior contain a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition or execute arbitrary code.
This vulnerability exists due to an integer overflow error within the code for handling PE format files. An unauthenticated, remote attacker can exploit this vulnerability by sending a crafted PE file to the vulnerable system. When the file is scanned, it could trigger a buffer overflow condition. This may allow the attacker to crash the affected service or potentially to execute arbitrary code with the privileges of the ClamAV service.
Proof-of-concept code is available.
Clam AntiVirus confirmed this vulnerability with a changelog and released updated software.
Indicators of Compromise
ClamAV versions 0.88.4 and prior are vulnerable.
This vulnerability exists within the libclamav/rebuildpe.c code for handling PE format files. An unauthenticated, remote attacker could exploit this vulnerability by sending a crafted PE file designed to trigger an integer overflow. When this file is scanned, the values of certain overly large variables can cause an integer overflow. This overflow results in the allocation of less memory than expected and may cause a heap-based buffer overflow. This exploitable condition may allow an attacker to crash the affected service or potentially to execute arbitrary code with the privileges of the ClamAV service.
To exploit this vulnerability, an attacker must deliver a PE format file to the affected system, likely as an e-mail attachment.
If ClamAV is being used to scan files on a mail gateway, any mail that contains an appropriately crafted PE file could cause ClamAV to cease scanning files for infections. Administrators may consider configuring ClamAV to restart in the event of a crash. However, because code execution is also a possibility, administrators using this configuration are advised to apply the updated version to avoid a possible compromise.
Administrators are advised to update to ClamAV version 0.88.5 or later.
Administrators may consider disabling PE file scanning; however, because all PE files are Windows executables, this mitigation is not practical on mail gateways to sites that use Windows desktops. Sites using other client operating systems may consider disabling scanning.
Administrators may consider blocking PE files from entering the network until updates are applied.
Administrators are advised to monitor affected systems for signs of exploitation.
Administrators are advised to configure ClamAV to restart in the event of an application crash.
Clam AntiVirus has released a software changelog at the following link: 0.88.5 Changelog
Apple has released a security update and updated software to address the PE file rebuild buffer overflow vulnerability in ClamAV.
2006-November-29 12:20 GMT
CyberGuard has provided release notes and an updated version of the SnapGear firmware to address the PE file rebuild buffer overflow vulnerability in ClamAV.
2006-November-01 10:46 GMT
Gentoo has released a security advisory and updated packages to address the PE file rebuild buffer overflow vulnerability in ClamAV.
2006-October-24 20:38 GMT
SUSE has released a security announcement and updated packages to address the ClamAV PE file rebuild buffer overflow vulnerability.
2006-October-20 12:47 GMT
Debian has released a security advisory and updated packages to address the ClamAV PE file rebuild buffer overflow
2006-October-20 10:15 GMT
Mandriva and Trustix have released security advisories and updated packages to address the ClamAV PE file rebuild buffer overflow vulnerability. FreeBSD has released an updated package within the ports collection. Proof-of-concept code is available.
2006-October-18 14:33 GMT
ClamAV contains an issue that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition or execute arbitrary code. Updates are available.
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Cisco Multivendor Vulnerability Alerts respond to vulnerabilities identified in third-party vendors' products. These alerts contain information compiled from diverse sources and provide comprehensive technical descriptions, objective analytical assessments, workarounds and practical safeguards, and links to vendor advisories and patches.