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Pacman (security vulnerability)

The Pacman vulnerability, discovered in 2022, is a type of memory safety vulnerability that exploits a weakness in Apple's pointer authentication codes (PACs) implementation on ARM-based processors, specifically those in the M1 series. PACs are a hardware-based security feature designed to protect against return-oriented programming (ROP) and jump-oriented programming (JOP) attacks by cryptographically signing pointers and verifying these signatures before the pointer is used.

The vulnerability allows an attacker to bypass PACs without leaving any traces in the system's logs. This is achieved by utilizing a hardware feature called "speculative execution," which allows the processor to execute instructions ahead of time, potentially before knowing if they are even needed. An attacker can craft a sequence of instructions that speculatively execute, leaking the PAC value associated with a pointer. Because this leakage occurs speculatively, the actual verification process doesn't fail, and the process continues as if the PAC was valid.

The primary impact of Pacman is that it allows attackers to bypass memory protections, enabling them to execute arbitrary code and potentially gain control of the system. The vulnerability can be exploited in various scenarios, potentially affecting any software running on vulnerable hardware.

While the Pacman vulnerability is not directly exploitable from JavaScript in a web browser, it could be triggered by native code (e.g., via a WebAssembly module) that interacts with vulnerable components or libraries.

It's important to note that the Pacman vulnerability requires the attacker to have the ability to execute code on the targeted system, meaning it cannot be exploited remotely without some other initial vulnerability allowing for code execution.

Mitigation strategies primarily focus on software-level defenses, as the underlying hardware vulnerability cannot be patched directly. Developers need to implement robust memory safety practices and be mindful of speculative execution side channels. Apple has released software updates and guidance to mitigate the impact of the Pacman vulnerability. These mitigations typically involve limiting speculative execution and implementing stricter checks on pointer values. The effectiveness of mitigations depends on the specific software environment and the attacker's capabilities.