Multiple Vendor Unusual MIME Encoding Content Filter Bypass

Type securityvulns
Reporter Securityvulns
Modified 2006-12-08T00:00:00


Several e-mail virus scanners can be tricked into passing an EICAR test file if the following conditions are met:

  1. the EICAR file is encoded in Base64 including characters not in the standard alphabet (e.g. whitespaces) and
  2. the part containing the EICAR file is nested within one or several levels of multipart/mixed content.

Details and PoC can be found at:

Vulnerable products: - BitDefender Mail Protection for SMB 2.0 - ClamAV 0.88.6 - F-Prot Antivirus for Linux x86 Mail Servers 4.6.6 - Kaspersky Anti-Virus for Linux Mail Server 5.5.10

Not recognizing the EICAR file, but aborting the scan: - F-Secure Anti-Virus for Linux Gateways 4.65

Not vulnerable: - avast! for Linux/Unix Servers 2.0.0