Skip to main content

Microsoft reveals rare 'wormable' bug found in Windows servers - with maximum severity rating

(Image credit: Shutterstock / hywards)

Microsoft has issued a patch for a critical vulnerability found to affect nearly all Windows DNS Server versions.

As confirmed by a blog post from Microsoft Security Response Center, the remote code execution (RCE) flaw is classified as “wormable” for its capacity to let malware spread across the entirety of a corporate network, with crippling effects.

It was handed the maximum severity score of 10.0 by the Common Vulnerability Scoring System (CVSS), highlighting the significant and immediate nature of the threat.

The flaw does not affect Windows 10 nor any other consumer implementation - only Windows DNS Server deployments.

'Wormable' Windows flaw

The Windows DNS Server vulnerability was first identified by security researchers at Check Point, who disclosed their discovery to Microsoft in May.

“A DNS server breach is a very serious thing. There are only a handful of these vulnerability types ever released,” said Omri Herscovici, Research Team Leader at Check Point.

“Every organization big or small using Microsoft infrastructure is at major security risk, if left unpatched. The risk would be a complete breach of the entire corporate network.”

Microsoft has now issued a patch for all Windows DNS Server versions, which system administrators are advised to apply immediately - although it is thought the bug is yet to be exploited in the wild.

“Wormable vulnerabilities have the potential to spread via malware between vulnerable computers without user interaction. Windows DNS Server is a core networking component,” explained Mechele Gruhn of Microsoft Security Response Center.

“While this vulnerability is not currently known to be used in active attacks, it is essential that customers apply Windows updates to address this vulnerability as soon as possible.”

Gruhn goes on to explain that, if circumstances mean an update is impractical, a workaround is available that does not involve restarting the server. Administrators that lean on the automatic updates facility, meanwhile, need take no further action. 

Via The Verge