CVE-2026-78422 zbus_polkit: polkit authorization bypass via PID reuse due to incorrect D-Bus type for the subject UID
A local attacker can bypass polkit authorization checks via a PID reuse race condition, gaining unauthorized privileges.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-78422?
CVE-2026-78422 is a high-severity vulnerability in z-galaxy zbus_polkit, published on 31 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
Subject::new_for_owner() in the zbus_polkit crate encodes the uid entry of a unix-process polkit subject as an unsigned 32-bit integer (D-Bus type u), whereas the org.freedesktop.PolicyKit1.Authority interface specifies a signed 32-bit integer (D-Bus type i). Because of this type mismatch, polkit silently discards the caller-supplied UID and instead determines the subject's owner itself by looking up the PID in /proc, a lookup that is inherently subject to a time-of-check/time-of-use race.
Consequently, an application that passes a UID obtained from a trustworthy source — for example SO_PEERCRED Unix socket peer credentials — in order to defend against PID reuse receives no protection, and the supplied UID has no effect on the authorization decision. A local unprivileged attacker who can cause an authorized process to terminate and then win the race to have their own process assigned the same PID can be authorized under the identity of the terminated process, bypassing the polkit authorization check and performing actions the attacker is not entitled to.
This issue affects zbus_polkit before 5.1.0.
Which versions are affected by CVE-2026-78422?
1 open source package ship an affected version, including zbus_polkit.
| Package | Affected | Fixed in |
|---|---|---|
zbus_polkit crates.io | From 0.0.0-0 | 5.1.0 |
How do I fix CVE-2026-78422?
Upgrade zbus_polkit to 5.1.0 or later.
Is CVE-2026-78422 being exploited?
There is no known exploitation of CVE-2026-78422 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-78422, GHSA-j48v-cvqq-xcv6, RUSTSEC-2026-0278, UBUNTU-CVE-2026-78422.