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Multiple Vendor Antivirus Products Malformed ZIP Attachment Scan Evasion Vulnerability

Multiple antivirus products from various vendors are reported prone to a vulnerability that may allow potentially malformed ZIP archives to bypass detection.

This issue arises when an affected application processes a ZIP archive with an invalid CRC-32 checksum. It should be noted that affected software may possibly detect a malicious file in the archive when it is decompressed or scanned manually.

The discoverer of this vulnerability has reported that this issue affects H+BEDV AntiVir, AVG Anti-Virus, Sybari Antigen for Microsoft Exchange, and products by McAfee, and BitDefender. Symantec products were not found to be vulnerable to the issue.

**Update: Symantec believes that the impact of this issue is low. This is because an archive handler processing an archive that possesses a corrupt CRC-32 checksum will fail, reporting that the archive is corrupt. This would mean that a malicious file contained in such an archive would not be directly accessible to a target recipient user.

Alternatively, if the CRC-32 checksum is corrected manually by the recipient user and the file is extracted, it will likely be detected by client-side Anti-Virus solutions during the file extraction routine. This detection will likely occur before the malicious file is directly processed by the end user.