PackageKit is a D-Bus abstraction layer that allows the user to manage packages in a secure way using a cross-distro, cross-architecture API. PackageKit between and including versions 1.0.2 and 1.3.4 is vulnerable to a time-of-check time-of-use (TOCTOU) race condition on transaction flags that allows unprivileged users to install packages as root and thus leads to a local privilege escalation. This is patched in version 1.3.5.

A local unprivileged user can install arbitrary RPM packages as root, including executing RPM scriptlets, without authentication. The vulnerability is a TOCTOU race condition on transaction-cached_transaction_flags combined with a silent state-machine guard that discards illegal backward transitions while leaving corrupted flags in place. Three bugs exist in src/pk-transaction.c: 1.

Unconditional flag overwrite (line 4036): InstallFiles() writes caller-supplied flags to transaction-cached_transaction_flags without checking whether the transaction has already been authorized/started. A second call blindly overwrites the flags even while the transaction is RUNNING. 2. Silent state-transition rejection (lines 873-882): pk_transaction_set_state() silently discards backward state transitions (e.g. RUNNING - WAITING_FOR_AUTH) but the flag overwrite at step 1 already happened.

The transaction continues running with corrupted flags. 3. Late flag read at execution time (lines 2273-2277): The scheduler's idle callback reads cached_transaction_flags at dispatch time, not at authorization time. If flags were overwritten between authorization and execution, the backend sees the attacker's flags.