TITLE: avast! Anti-Virus Engine Malformed ZIP/CAB Archive Virus Detection Bypass SECUNIA ADVISORY ID: SA17126 VERIFY ADVISORY: http://secunia.com/advisories/17126/ CRITICAL: Not critical IMPACT: Security Bypass WHERE: >From remote SOFTWARE: avast! for Kerio 4.x http://secunia.com/product/5852/ DESCRIPTION: fRoGGz has discovered a weakness in avast! Anti-Virus scan engine, which can be exploited by malware to bypass certain scanning functionality. The weakness is caused due to an error in parsing certain malformed archives and can be exploited via a specially crafted archive with additional characters prepended to the header. Such malformed archives can be correctly extracted by some archiving software. Successful exploitation allows malware packed in malformed archives to pass the email anti-virus scanning gateway undetected. The weakness has been confirmed in avast! for Kerio version 4.6.313 (Vps 0541-1) when scanning an email containing malformed ".zip" and ".cab" archives. Other versions may also be affected. NOTE: This is not an issue on client systems, as the malware is still detected upon execution by the desktop on-access scanner. SOLUTION: Desktop on-access scanner should be used to ensure that the malware is detected upon extraction. Filter all compressed file archives at border gateways if they are not required. PROVIDED AND/OR DISCOVERED BY: fRoGGz, SecuBox Labs ORIGINAL ADVISORY: http://shadock.net/secubox/AVCraftedArchive.html ---------------------------------------------------------------------- About: This Advisory was delivered by Secunia as a free service to help everybody keeping their systems up to date against the latest vulnerabilities. Subscribe: http://secunia.com/secunia_security_advisories/ Definitions: (Criticality, Where etc.) http://secunia.com/about_secunia_advisories/ Please Note: Secunia recommends that you verify all advisories you receive by clicking the link. Secunia NEVER sends attached files with advisories. Secunia does not advise people to install third party patches, only use those supplied by the vendor. ---------------------------------------------------------------------- Unsubscribe: Secunia Security Advisories http://secunia.com/sec_adv_unsubscribe/?email=packet%40packetstormsecurity.org ----------------------------------------------------------------------