CVE-2026-41651

PackageKit is a 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 schedulers 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 attackers flags.

Weakness

The product checks the state of a resource before using that resource, but the resource’s state can change between the check and the use in a way that invalidates the results of the check.

Affected Software

Potential Mitigations

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/27.html
• https://cwe.mitre.org/data/definitions/29.html

References

• https://github.com/PackageKit/PackageKit/blob/04057883189efa225a7c785591aa87cb299782f8/src/pk-transaction.c#L2273-L2277
• https://github.com/PackageKit/PackageKit/blob/04057883189efa225a7c785591aa87cb299782f8/src/pk-transaction.c#L4036
• https://github.com/PackageKit/PackageKit/blob/04057883189efa225a7c785591aa87cb299782f8/src/pk-transaction.c#L873-L882
• https://github.com/PackageKit/PackageKit/security/advisories/GHSA-f55j-vvr9-69xv
• https://github.security.telekom.com/2026/04/pack2theroot-linux-local-privilege-escalation.html
• http://www.openwall.com/lists/oss-security/2026/04/22/6