The government security agency says it is aware of a stack buffer overflow vulnerability in the way that Microsoft Access handles specially crafted database files.
Opening a specially crafted Microsoft Access Database file (".MDB") can cause arbitrary code execution without requiring any additional user interaction, said CERT.
As Microsoft Access files are considered to be high-risk, it may also be possible to execute arbitrary code without using a vulnerability in Microsoft Access, said CERT.
"US-CERT is aware of active exploitation using malicious Microsoft Access databases," said the agency.
CERT said users should not open attachments from unsolicited e-mail messages, and should block high-risk file attachments at e-mail gateways.