The problem lies in computer routers and other networking equipment that use a commonly employed standard known as Universal Plug and Play or UPnP.
UPnP makes it easy for networks to identify and communicate with equipment, reducing the amount of work it takes to set up networks.
Security software maker Rapid7 said in a white paper to be released Tuesday that it discovered between 40 million and 50 million devices that were vulnerable to attack due to three separate sets of problems that the firm's researchers have identified with the UPnP standard.
The long list of devices includes products from manufacturers including Belkin, D-Link, Cisco Systems Inc's Linksys division and Netgear.
Representatives for Belkin, D-Link, Linksys and Netgear could not be reached for comment on Monday evening.
Chris Wysopal, chief technology officer of security software firm Veracode, said he believed that publication of Rapid7's findings would draw widespread attention to the still emerging area of UPnP security, prompting other security researchers to search for more bugs in UPnP.
"This definitely falls into the scary category," said Wysopal, who reviewed Rapid7's findings ahead of their publication.
"There is going to be a lot more research on this. And the follow-on research could be a lot scarier."
Rapid7 has privately alerted electronics makers about the problem through the CERT Coordination Center, a group at the Carnegie Mellon Software Engineering Institute that helps researchers report vulnerabilities to affected companies.
"This is the most pervasive bug I've ever seen," said HD Moore, chief technology officer for Rapid7.
He discussed the research with Reuters late on Monday.
Moore, who created a widely used platform known as Metasploit that allows security experts to simulate network attacks, said that he expected CERT to release a public warning about the flaw on Tuesday.
A spokesman for the CERT Coordination Center declined to comment.
A source with a networking equipment maker confirmed they had been alerted that CERT would issue an advisory on Tuesday and that companies were preparing to respond.
Taking control The flaws could allow hackers to access confidential files, steal passwords, take full control over PCs as well as remotely access devices such as webcams, printers and security systems, according to Rapid7.
Moore said that there were bugs in most of the devices he tested and that device manufacturers will need to release software updates to remedy the problems. He said that is unlikely to happen quickly.
In the meantime, he advised computer users to quickly use a free tool released by Rapid7 to identify vulnerable gear, then disable the UPnP functionality in that equipment.
Moore said hackers have not widely exploited the UPnP vulnerabilities to launch attacks, but both Moore and Wysopal expected they may start to do so after the findings are publicised.
Still, Moore said he decided to disclose the flaws in a bid to pressure equipment makers to fix the bugs and generally pay more attention to security.
People who own devices with UPnP enabled may not be aware of it because new routers, printers, media servers, Web cameras, storage drives and "smart" or Web-connected TVs are often shipped with that functionality turned on by default.
"You can't stay silent about something like this," he said.
"These devices seem to have had the same level of core security for decades. Nobody seems to really care about them."
Veracode's Wysopal said that some hackers have likely already exploited the flaws to launch attacks, but in relatively small numbers, choosing victims one at a time.
"If they are going after executives and government officials, then they will probably look for their home networks and exploit this vulnerability," he said.
Rapid7 is advising businesses and consumers alike to disable UPnP in devices that they suspect may be vulnerable to attack.
The firm has released a tool to help identify those devices on its website http://www.rapid7.com.
(Editing by Edmund Klamann and Robert Birsel)
I'm not in Pakistan to seek job: Moores
Chris Gayle is world's best T20 cricketer: Shane Watson
Cisco, CERT-In sign MoU
Chris Gayle lives up to his Twitter remark
Kindle Fire HD tablets: Are these iPad killers?