Apple Will Patch Mobile Safari's PDF Flaw in 'Forthcoming' Update

Apple said it will fix the PDF bug in Safari, which could be exploited to infect iOS devices with malware that gives attackers administrative access to passwords, applications and personal data.

Apple is working on a fix for the security vulnerability that could potentially allow attackers to remotely takeover iPhones, iPads and iPod Touches.

The security flaw allows attackers to infect users' iOS devices with malicious software that would give them administrator privileges just by displaying infected PDF files, the German Federal Office for Information Security warned July 6. Apple did not provide a timeline for the software update that would patch the vulnerability.

Once the device is successfully infected, the attacker could access confidential data such as passwords, online-banking data, calendars, geo-location and emails, as well as intercept telephone conversations, Germany's information security agency warned.

"Apple takes security very seriously; we're aware of this reported issue and developing a fix that will be available to customers in an upcoming software update," the company said in a statement on July 7.

The hole was exposed in JailbreakMe 3.0, a freely available tool used to unlock iOS devices to run non-Apple-approved applications. The latest version of the software, released July 5, exploits a flaw in the way Apple's Mobile Safari Web browser loads PDF files to allow users to easily jailbreak their devices just by visiting the site. Security experts warned that the same vulnerability could be used maliciously.

"If visiting the JailBreakMe Website with Safari can cause a security vulnerability to run the site's code, just imagine how someone with more nefarious intentions could also abuse the vulnerability to install malicious code on your iPad or iPhone," Graham Cluley, a technology consultant at Sophos, wrote on the NakedSecurity blog.

Cyber-criminals can create booby-trapped Web pages that could, if visited by an unsuspecting user, run code on the iOS devices, according to Cluley. Apple needs to close this zero-day vulnerability immediately because leaving it open is "simply inviting malicious hackers to exploit it," he said.

A hacking group calling itself the iPhone Dev-Team is behind JailbreakMe, and the vulnerability was discovered by one of its developers, "Comex." Comex was able to circumvent two security features built into iOS that are supposed to prevent attackers from remotely executing code: ASLR (Address Space Layout Randomization) and DEP (Data Execution Prevention).

ASLR, also found in Windows and OS X, randomizes the location of key components in the memory address space. This makes it harder for attackers to find the memory stacks and heaps in which to run malicious code. DEP blocks buffer overflows that can be used to load and execute unauthorized code.

The security bug does not exist on Mac OS X.

JailbreakMe is giving a "blueprint" to hackers on how to infect devices with malware, Cluley said. The Dev-Team doesn't think so, writing in the FAQ that the flaw has "long been present and exploitable."

"I did not create the vulnerabilities, only discover them," according to the FAQ page.

Comex has issued his own patch for the hole, which can be applied after running the JailbreakMe tool. The patch is available as PDF Patcher 2 on the Cydia application store, where users can download applications that run only on jail-broken devices.

"Normally, I say, for security purposes, don't jailbreak, but for now I say, jailbreak and install pdfpatch2 from Cydia," security researcher Charlie Miller wrote on Twitter.

Ironically, that means users who run JailbreakMe and apply the patch will actually be safer than the rest of the users waiting for the official fix from Apple.

"Users are advised to avoid downloading or viewing PDF files from untrusted sources on their iOS devices," Intego researchers suggested on the Mac Security Blog.

Jailbreaks make iOS more secure in the long run, the JailbreakMe FAQ suggests, since Apple learns about zero-day flaws it wouldn't have known about otherwise and can fix them before cyber-criminals can come up with a malicious exploit. The Dev-Team exploited a different zero-day vulnerability in the iPhone's mobile Safari browser about a year ago to create an earlier version of JailbreakMe. Apple moved quickly to close that vulnerability.

Apple generally addresses jailbreaking flaws pretty quickly, so it's likely this exploit will remain "theoretical," the team wrote on the FAQ page.

Apple has been claiming jailbreaking was illegal since 2009 and voided the warranty on its devices. However, the United States Copyright office ruled in mid-2010 that bypassing a manufacturer's protection measures to run "lawfully obtained" software applications was permissible. Jailbreaking usually requires owners to connect the device to a computer in order to run the software, but the latest "untethered" method would allow even casual users to crack the operating system from the Website.