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Apple emergency patches fix zero-click iMessage bug used to inject NSO spyware

Apple on Monday issued security patches for its mobile and desktop operating systems, and for its WebKit browser engine, to address two security flaws, at least one of which was, it is said, used by autocratic governments to spy on human rights advocates.

A day before the iGiant is expected to announce the iPhone 13, it released updates for iOS 14.8 and iPadOS 14.8, watchOS 7.6.2, and macOS Big Sur 11.6. Previous macOS releases Catalina (10.15) and Mojave (10.14) received updated versions of WebKit-based Safari (14.1.2), with Catalina also getting a supplemental fix.

One of the bugs, CVE-2021-30860, resides in Apple’s CoreGraphics framework. Reported by researchers at University of Toronto’s Citizen Lab, the bug consists of an integer overflow that allows a malicious PDF file to achieve arbitrary code execution, allowing spyware and other malicious programs to run.

Apple is aware of a report that this issue may have been actively exploited

“Apple is aware of a report that this issue may have been actively exploited,” the biz said in its terse, non-committal summary.

Citizen Lab managed to be less coy in its assessment. On August 24, 2021, researchers with the organization reported that the iPhones of nine Bahraini activists had been hacked between June 2020 and February 2021 using NSO Group’s Pegasus spyware and two zero-click iMessage exploits.

One was the KISMET exploit identified last year, which affected iOS prior to version 14. The other more recently identified vulnerability is called FORCEDENTRY by Citizen Lab and Megalodon by Amnesty International’s security group. The name FORCEDENTRY is a reference to the exploit’s ability to bypass a defense Apple implemented in iOS 14 called Blast Door that was supposed to safeguard iMessage traffic. The messaging exploit is believed to have been in use since February 2021.

“When the FORCEDENTRY exploit was being fired at a device, the device logs showed crashes associated with IMTranscoderAgent,” the Citizen Lab report explains. “The crashes appeared to be segfaults generated by invoking the copyGifFromPath:toDestinationPath:error function on files received via iMessage.”

The crashes arose when using CoreGraphics to decode JBIG2-encoded data within a PDF file prepped to trigger the bug. When targeted activists received these poisoned PDF files – which had a .gif file extension but were in fact Adobe PDF files containing a JBIG2-encoded stream – no further action was required to infect the victim’s device with malicious code: they simply had to receive the message. According to Citizen Lab, the FORCEDENTRY exploit, when successful, installed NSO Group’s Pegasus spyware.

“Our latest discovery of yet another Apple zero day employed as part of NSO Group’s arsenal further illustrates that companies like NSO Group are facilitating ‘despotism-as-a-service’ for unaccountable government security agencies,” Citizen Lab researchers said in a post on Monday. “Regulation of this growing, highly profitable, and harmful marketplace is desperately needed.”

The other bug patched by Apple, CVE-2021-30858, was reported by an unidentified researcher. Dubbed “Synoptic Acanthopterygian” by Vulnonym, it’s a use-after-free vulnerability that allows malicious web content processed by Apple’s WebKit rendering engine – which Apple requires all browsers on iOS to use – to execute arbitrary code.

Apple said this flaw too may also be under active exploitation, though it provides no further detail.

The Register asked Apple to comment and the company, ever concerned that its customers should be well-informed, did not respond. ®