A Chrome browser vulnerability known under the CVE-2018-6177 identifier, recently discovered by Imperva researcher Ron Masas, was just patched by Google. The security flaw could allow an attacker to retrieve sensitive data from websites using audio or video HTML tags.
Technical Details of CVE-2018-6177
In his discovery, Masas “was able to use the video/audio html5 tags to get a pretty good estimation of a cross origin resource size, since there is no validation on the resource content type it is possible to estimate any resource”.
The researcher also discovered that, by engineering sites to return a diffеrent response size depending on the currently logged user properties, it is possible to use this method to extract valuable information:
For example if a social networking site allow his users to create public posts to a specific audience, let’s say only for people in the age of 24. an attacker can create multiple posts for each age; Then using hidden video tags he could request each resource; since using this method give us an estimation of the resource size it would be possible for an attacker to extract the currently logged social networking user site exact age in seconds, the researcher said.
How Is CVE-2018-6177 Exploited
CVE-2018-6177 can be exploited in older versions of Chrome. Exploit is possible in cases where an attacker successfully tricks a potential victim to visit a malicious site. As explained by the researcher, a typical attack scenario would require malicious code that loads content from legitimate sites inside audio and video HTML tags.
This usually happens via malvertising techniques or via vulnerabilities on legitimate sites which allow attackers to inject and execute malicious code. The second type of attack occurs with the help of stored cross-site scripting flaws (XSS).
Fortunately, the bug has already been fixed at the end of July with the release of Chrome v68.0.3440.75.