Pierluigi Paganini
November 21, 2022
Researcher Wojciech Reguła (@_r3ggi) of SecuRing published technical details and proof-of-concept (PoC) code for a macOS sandbox escape vulnerability tracked as CVE-2022-26696 (CVSS score of 7.8).
In a wrap-up published by Regula, the researcher observed that the problem is caused by a strange behavior he observed in a sandboxed macOS app that may launch any application that won’t inherit the main app’s sandbox profile.
According to ZDI, This vulnerability allows remote attackers to escape the sandbox on affected installations of Apple macOS. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability.
“A sandboxed process may be able to circumvent sandbox restrictions.” reads the advisory published by Apple that addressed the flaw with improved environment sanitization.
According to ZDI, a remote attacker can trigger the flaw to escape the sandbox on vulnerable Apple macOS installs. ZDI pointed out that an attacker can exploit the bug only he has first obtained the ability to execute low-privileged code on the target system.
“This vulnerability allows remote attackers to escape the sandbox on affected installations of Apple macOS. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability.” reads the report published by ZDI. “The specific flaw exists within the handling of XPC messages in the LaunchServices component. A crafted message can trigger execution of a privileged operation. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of the current user.”
The issue was reported to the vendor on December 22, 2021 and it was disclosed on August 15, 2022.
Regula focused his analysis on an Objective-C method of the Terminal.app.
“+[TTApplication isRunningInInstallEnvironment] will return YES when the __OSINSTALL_ENVIRONMENT environment variable was set.” wrote the expert. “So, when Terminal.app starts, some of the environment variables were not cleared when +[TTApplication isRunningInInstallEnvironment] returned YES. Great, with simple command injection I was able to execute code within the Terminal.app context without any sandbox!”
The expert was able to weaponize the flaw by embedding the exploit in a Word document and load the Mythic’s JXA payload.
“Executing code within the Terminal.app context can be really dangerous as it can also have some TCC permissions already granted.” Regula explained.
Reguła shared a video PoC that demonstrates how to weaponize Word document to escape the sandbox and execute code within the Terminal.
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(SecurityAffairs – hacking, macOS Sandbox Escape)
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