Adobe's ColdFusion web development software is to blame for the downtime of the US Government's National Vulnerability Database.
The malware infected two servers, and caused the National Institute for Standards and Technology to take the NVD database and other US government sites offline on Friday.
The servers were compromised for at least two months before a firewall detected mysterious outbound traffic. The malware used vulnerabilities in Adobe ColdFusion, for which a patch is now available.
It gave the patch a priority-one rating, and said it was aware the vulnerabilities were being used in the wild.
"The servers were compromised before the software vulnerability was known to the software vendor," director of NIST's public affairs office Gail Porter, told The Register.
NIST first learned that its server had been compromised through firewall alerts that were detected on Friday.
The four vulnerabilities that the patch dealt with could allow hackers to gain administrative access to the server, along with access to restricted directories.
Two servers were taken offline – one hosted NIST's NVD database, while the other hosted a variety of government websites, including manufacturing.gov, e3.gov, greensuppliers.gov, emtoolbox.nist.gov, nsreserve.gov, and stonewall.nist.gov.
"Manufacturing.gov has been restored on a different server," Porter said. "NIST is working to restore the other websites as quickly as possible." ®