This post was authored by Earl Carter & Yves Younan.

Talos is constantly researching the ways in which threat actors take advantage of security weaknesses to exploit systems. Use-after-free vulnerabilities have become an important class of security problems due to the existence of mitigations that protect against other types of vulnerabilities, such as buffer overflows. Today, Talos is releasing FreeSentry, a mitigation for use-after-free vulnerabilities.

FreeSentry works as a plugin for LLVM with an associated runtime library that tracks pointers when they are set to objects and invalidates them when the memory associated with that object is freed. Our initial approach was published at the 2015 Network and Distributed System Security (NDSS) Symposium in February. The paper can be downloaded here. At CanSecWest 2015, Yves Younan of Talos presented an enhanced version of FreeSentry which included further developments, such as porting the original mitigation from C Intermediate Language (CIL) to LLVM. The CanSecWest slides are available here. Note that the LLVM performance numbers in the CanSecWest presentation were preliminary numbers, and have been updated for this post.

Continue reading “Research Spotlight: FreeSentry Mitigating use-after-free Vulnerabilities”