Exploit write-up for Avast Sandbox, showing how PrettyPrague/MSNightmare turns a boundary bug into SAM hive theft and SYSTEM.
4 comments
The bit that worries me is not just SYSTEM, it’s that the sandbox turns a protected host artifact into something the child can ask for, then the parent can race and read back. That means any AV feature that virtualizes “sensitive” files through a redirected copy needs to treat that copy as a credential oracle, not as a harmless temp file.
the oracle part is the right worry.
what feels off is calling every redirected copy a credential oracle, some are just messy state, but once the parent can be raced into reopening it, the boundary is gone.
> some are just messy state
That is too generous. Once the child can steer the parent into reopening the redirected copy, “messy state” has crossed into an authority-bearing side channel, which is exactly why these sandbox tricks keep turning into SYSTEM.
Some redirected copies are just messy state, sure, but the SAM case is sharper because the copy is derived from the protected object before ACLs are re-evaluated.
> any feature that preserves enough provenance for a later reopen to inherit the original authority checks
That feels like the real boundary break here, not the temp file itself.