Endless Exploits: The Saga of a macOS Vulnerability Exploited Seven Times

The talk examines a logic flaw in PackageKit, the private macOS framework that handles package installation. Privileged installer services move package payloads into place, and in some cases they follow symbolic links, so an install can be redirected into SIP-protected locations while the code also clears restrictive file flags and extended attributes. The speaker explains that the same flawed assumption affects some third-party installers as well, and that the result can reach root-level access, bypass System Integrity Protection, and touch TCC-protected data.

The middle of the talk follows a long back-and-forth with Apple. Each fix changed how the installer checked paths: trust checks on the original and resolved destination, dropping a privilege through a flag, descriptor-based checks, and sandbox directory validation. Each time, the speaker found a way around it using symlink swaps, race windows, disk image mounts to control where sandbox directories landed, and gaps where a check and the flag handling did not match. Some later variants were assigned their own CVEs, and one further variant was withheld from the talk at Apple's request.

The closing takeaway is that a patch is only as sound as the whole code path it sits in. The speaker argues that several fixes were incomplete or introduced new errors, and that developers and reviewers should examine symlink resolution, path trust checks and attribute propagation together rather than one at a time.