Google researchers have discovered a major vulnerability in the SSL encryption technology that could allow hackers to take control of users’ email accounts, online banking and other services.
Dubbed Poodle (Padding Oracle On Downloaded Legacy Encryption), the flaw in the design of the obsolete though still widely used SSL version 3.0 allows the attacker to calculate the plaintext of secure connections.
“SSL 3.0 is nearly 15 years old, but support for it remains widespread,” Bodo Möller, Google’s security researcher who discovered the vulnerability together with Thai Duong and Krzysztof Kotowicz, said in a blog on Google’s website.
“Most importantly, nearly all browsers support it and, in order to work around bugs in HTTPS servers, browsers will retry failed connections with older protocol versions including SSL 3.0. Because a network attacker can cause connection failures, they can trigger the use of SSL 3.0 and then exploit this issue.”
SSL (Secure Socket Layers) is a standard security technology for establishing an encrypted link between a server and a client – a web server and browser or mail server and mail client.
To mitigate the issue, Google recommends disabling the SSL 3.0 protocol completely and implementing the TLS_FALLBACK_SCSV patch that prevents attackers from using connection failures to induce browsers to switch to obsolete protocols.
“Google Chrome and our servers have supported TLS_FALLBACK_SCSV since February and thus we have good evidence that it can be used without compatibility problems,” Möller wrote. “Additionally, Google Chrome will begin testing changes today that disable the fallback to SSL 3.0. This change will break some sites and those sites will need to be updated quickly.”
The Poodle vulnerability is the third major cyber security flaw identified by researchers this year. Following the Heartbleed bug in Open SSL and the Shellshock bug in a piece of Unic software known as Bash, the vulnerability discovered by Google has been identified as less threatening than the previous two.
"If Shellshock and Heartbleed were Threat Level 10, then Poodle is more like a 5 or a 6," said Tal Klein, vice president with cloud security firm Adallom.
Ivan Ristic, director of application security research with Qualys, said Poodle was not as serious as the previous threats because the attack was "quite complicated", requiring hackers to have privileged access to networks.
Jeff Moss, a cyber-adviser to the US Department of Homeland Security, said attackers would need to launch a "man-in-the-middle" attack, placing themselves between victims and websites using approaches such as creating rogue Wi-Fi "hotspots" in Internet cafes.
Other Internet companies have already said they would follow Google’s example and move away from SSL 3.0. Mozilla plans to disable the outdated protocol by default in the upcoming version of the Firefox browser, to be released on 25 November.
Microsoft issued an advisory suggesting that customers disable SSL 3.0 on Windows for servers and PCs.
Matthew Green, an assistant research professor of computer science at Johns Hopkins University said that disabling SSL 3.0 can be difficult for some computer users.
"It's not going to take out the infrastructure of the Internet. But it's going to be a hassle to fix," Green said.