Cisco zero-day vulnerability hits 40,000+ devices in a matter of days

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A Cisco zero-day vulnerability affecting its IOS XE Software has been found to have infected more than 41,000 devices, marking a significant increase in a matter of days.

There was previous speculation about the number of infected devices in the immediate wake of the vulnerability disclosure. 

The vulnerability, tracked as CVE-2023-20198, had already been exploited with backdoors installed on 34,104 devices, according to Censys’ findings. 

Originally, 50% of the 67,445 devices that use the Cisco web interface were thought to be infected. However, a further 7, 843 have been compromised by the vulnerability, bringing the total to over 41,000.

“Iterating on our current query to find potential targets, we updated it with some more generic conditionals, hoping to find even more potentially vulnerable hosts,” the Censys research team wrote in its blog. 

“Unfortunately, the updates were successful, and we found even more compromised hosts this morning.” 

Censys was able to tag devices that used Cisco web interfaces by deploying a new label, though that only noted whether they were running the Cisco IOS-WE web interface. 

A secondary scan using Censys data as a baseline and an open-source tool was used to analyze how widespread the vulnerability was.


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The firm’s research has highlighted particular concerns in the USA and the Philippines, which recorded the most compromised devices. 

It appears that the primary targets of the vulnerability are smaller businesses and individuals, rather than larger organizations. 

The zero-day vulnerability was first identified on 16 October and given a maximum CVSS rating of 10.0. 

Cisco explained that it specifically affected the user interface of its IOS XE Software and that it could be used to enable an unauthorized party to gain control over an affected system. This, it said, had already been exploited in the wild.

Bobby Hellard

Bobby Hellard is ITPro's Reviews Editor and has worked on CloudPro and ChannelPro since 2018. In his time at ITPro, Bobby has covered stories for all the major technology companies, such as Apple, Microsoft, Amazon and Facebook, and regularly attends industry-leading events such as AWS Re:Invent and Google Cloud Next.

Bobby mainly covers hardware reviews, but you will also recognize him as the face of many of our video reviews of laptops and smartphones.