Hours after developers revealed they had exploited bugs in Apple's iOS to "jailbreak" iPhones and iPads, German government security authorities warned that one of the flaws could be put to malicious use.
Malformed files that exploit the vulnerability have been publicly posted on the Internet.
Late Wednesday, Germany's Federal Office for Information Security, known by its German-language initials of BSI for "Bundesamt fuer Sicherheit in der Informationstechnik," warned citizens that the iOS bug could be used by criminals to hijack iPhones, iPads and iPod Touches.
"Even clicking a crafted PDF document or surfing to a website with the PDF documents are sufficient to infect the mobile device with malicious software," the BSI said in a translation of the German-language alert.
PDF files that successfully exploit the vulnerability are available on the Web, according to Mikko Hypponen, chief research officer of Helsinki-based antivirus company F-Secure.
And those PDFs could be used by miscreants to hack iOS devices simply by luring users to malicious sites, said Andrew Storms, director of security operations at nCircle Security.
iPhone and iPad users steered to a malicious PDF -- via a link embedded in an email, for instance -- would not receive any warning or be required to take additional action.
"This is a click-and-pwn kind of situation since the user is not prompted to confirm opening the file," said Storms, referring to the term used by researchers to describe hijacking a device.
The BSI warning came just hours after a group of developers released an updated version of JailbreakMe, a tool that hacks iOS so iPhone and iPad users can install software not sanctioned by Apple.
Those developers exploited a pair of vulnerabilities, including one in the font parsing of the PDF viewer integrated with the iOS version of Safari, and another that bypassed anti-malware defenses such as ASLR (address space layout randomization).
Wednesday, security experts said that the same vulnerabilities, particularly the one exploitable through malicious PDF files, could be used by criminals to hijack Apple's popular iPhone and iPad.
"They're certainly a threat, and would be easy to make malicious," said Charlie Miller, a noted Mac OS X and iOS vulnerability researcher who works for Denver-based Accuvant.
Miller also speculated that Apple would quickly patch the vulnerabilities, perhaps even faster than last year when it faced a similar situation. In August 2010, Apple patched a pair of bugs used by JailbreakMe 2.0 just 10 days after the tool's release.
News of JailbreakMe 3.0's impending release had leaked several days before Wednesday's official launch, noted Miller, and should have given Apple even more warning.
Yesterday's BSI alert was similar to one it issued last August after JailbreakMe 2.0 appeared.
On Thursday, Apple said it would fix the flaws.
"We're aware of this reported issue and developing a fix that will be available to customers in an upcoming software update," an Apple spokesman told the IDG News Service today.
Last year, Apple patched the Jailbreak 2.0 bugs six days after saying it was working on a fix.
Ironically, a patch is available, but only to those who have hacked their iPhone, iPad or iPod Touch with JailbreakMe 3.0. The fix, dubbed "PDF Patcher 2," can be downloaded by jailbroken devices from the Cydia app store.
The BSI was especially concerned that the vulnerability would be exploited by hackers to target specific individuals. Because iOS devices are often used by senior management, the agency warned, "It is possible that the weaknesses can be exploited for targeted attacks on leaders to get to confidential company information."
Often labeled, "spear phishing," such targeted attacks have become extremely effective for cyber criminals, who have used the tactic to infiltrate major corporations, including Google, and make off with proprietary data by the gigabyte, or have been aimed at senior officials in the U.S. government and the International Monetary Fund.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, or subscribe to Gregg's RSS feed . His e-mail address is email@example.com.