AVIRA: DESERIALIZE, DELETE, AND ESCALATE - THE PROPER WAY TO USE AN AV

Summary from the TLDR InfoSec newsletter

Quarkslab disclosed three vulnerabilities in Avira Internet Security (versions 1.1.109.1990 and below, fixed in 1.1.114.3113): CVE-2026-27748, a symlink-following arbitrary file delete in the Software Updater running as SYSTEM; CVE-2026-27749, an unfiltered .NET BinaryFormatter deserialization in System Speedup's RealTimeOptimizer that reads an attacker-controlled file from the user-writable ProgramData directory; and CVE-2026-27750, a TOCTOU folder delete in the Optimizer that enables the Config.msi junction trick for a SYSTEM shell. The file delete primitive chains into the deserialization bug when temp_rto.dat already exists and can't be overwritten, while the TOCTOU path plants HID.DLL via MSI rollback. The writeup also documents a contentious disclosure process in which Gen Digital refused to accept vulnerability reports outside its NDA-bound bug bounty platform.