Firefox 32 Brings Security Fixes, Public Key Pinning

Mozilla has released Firefox 32 for Windows, Linux, Mac and Android. In addition to some new features, the latest version of the Web browser also includes fixes for several security vulnerabilities and support for public key pinning.

Public key pinning helps protect users against man-in-the-middle (MitM) attacks and rogue certificate authorities (CAs) by allowing website operators to specify which CAs issue valid certificates for them, instead of accepting one of the hundreds of built-in root certificates that ship with the Web browser.

“If any certificate in the verified certificate chain corresponds to one of the known good (pinned) certificates, Firefox displays the lock icon as normal. When the root cert for a pinned site does not match one of the known good CAs, Firefox will reject the connection with a pinning error,” Sid Stamm, senior manager of security and privacy engineering at Mozilla, explained in a blog post. “This type of error can also occur if a CA mis-issues a certificate. In this way, key pinning can be used by sites to add another layer of trust to their servers’ deployment of TLS.”

The list of websites pinned in Firefox 32 consists of twitter.com and several Twitter subdomains, and the Mozilla subdomains addons.mozilla.{org,net}, cdn.mozilla.{org,net} and media.mozilla.com. With the next major Firefox release, Mozilla plans on adding Google and other Twitter subdomains. In Firefox 34, the company wants to include the Firefox “accounts” subdomain, Tor and Dropbox.

According to Monica Chew, lead privacy engineer at Mozilla, Firefox 32 and future versions support built-in pins, which means that the list of acceptable CAs must be set at the time of build for each domain.

“Pinning is enforced by default. Sites may advertise their support for pinning with the Public Key Pinning Extension for HTTP, which we hope to implement soon,” Chew said.

As far as security fixes are concerned, a total of six vulnerabilities have been patched with the release of Firefox 32. One of the critical flaws was reported by the security researcher regenrecht, who found a use-after-free flaw during text layout when interacting with the setting of text direction. The vulnerability can be exploited for arbitrary code execution.

A use-after-free issue during DOM interactions with SVG content was reported by Abhishek Arya of the Google Chrome Security Team. The flaw can lead to a potentially exploitable crash. Miscellaneous memory safety hazards identified by Mozilla developers have also been addressed in Firefox 32.

The high-impact vulnerabilities are a profile directory file access through the “file:” protocol (affects only the Android version), and an uninitialized memory use issue during GIF rendering. The latter vulnerability was discovered by Google security researcher Michal Zalewski, a.k.a. lcamtuf. Zalewski has published the details on this vulnerability on his personal blog and on the Full Disclosure mailing list.

A moderate-impact out-of-bounds read issue during the creation of an audio timeline in Web Audio has also been fixed. The vulnerability can lead to a crash and could allow for the reading of random memory values, Mozilla said.

In July, Mozilla announced that starting with Firefox 31, the malware detection system in the Web browser has been expanded to include downloaded files, not just websites as before. While Mozilla is making considerable efforts to keep Firefox users safe, the company accidentally exposed the details of tens of thousands of developers twice in the past month.

In early August, the company dumped the email addresses of 76,000 developers and 4,000 password hashes on a public server. Just a few days ago, Mozilla started warning those who contributed to testing Bugzilla builds that their email addresses and encrypted passwords were inadvertently posted to a public Web server.