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8.4
CVE-2026-78422: zbus_polkit lets local user gain unauthorized privileges
CVE-2026-78422 · published 2 months ago
Summary
The Rust library zbus_polkit (versions before 5.1.0) can be tricked into trusting the wrong process ID when checking a user's identity. An unprivileged user who forces a trusted program to stop and then reuses its process ID can be granted the same rights as that program. Update the library to version 5.1.0 or later to stop this from happening.
What to do
- Update debian rust-zbus-polkit to version 5.1.0-1.
- Update zeenix zbus_polkit to version 5.1.0.
- Update z-galaxy zbus_polkit to version 5.1.0 or later.
Affected software
| Ecosystem | Vendor | Product | Affected versions |
|---|---|---|---|
| Debian:14 | debian | rust-zbus-polkit |
< 5.1.0-1 Fix: upgrade to 5.1.0-1
|
| – | z-galaxy | zbus_polkit | < 5.1.0 |
| crates.io | zeenix | zbus_polkit |
>= 0.0.0-0, < 5.1.0 Fix: upgrade to 5.1.0
|
| Ubuntu:26.10 | canonical | rust-zbus-polkit | All versions |
Original advisory text
zbus_polkit: polkit authorization bypass via PID reuse due to incorrect D-Bus type for the subject UID
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.
References
- https://bugzilla.suse.com/show_bug.cgi?id=1277659 Third Party Advisory
- https://security-tracker.debian.org/tracker/CVE-2026-78422 Vendor Advisory
- https://crates.io/crates/zbus_polkit Product
- https://rustsec.org/advisories/RUSTSEC-2026-0278.html Vendor Advisory
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/78xxx/CVE-2026-78422... Vendor Advisory
- https://ubuntu.com/security/CVE-2026-78422 Third Party Advisory
- https://www.cve.org/CVERecord?id=CVE-2026-78422 Third Party Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2026-78422 Vendor Advisory
- https://github.com/z-galaxy/zbus_polkit Product
- https://github.com/z-galaxy/zbus_polkit/pull/101 Third Party Advisory
Internet-facing
14 days
Internal
At next upgrade
- Not known to be exploited
- Needs hands-on effort to exploit
- Gives an attacker full control
Severity
8.4
High
Type
CWE-686Function Call With Incorrect Argument Type
CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition
Timeline
Published31 Aug 2026
Updated26 Oct 2026
First seen31 Aug 2026
Sources
CVE-2026-78422 · NVD
CVE-2026-78422 · MITRE
DEBIAN-CVE-2026-78422 · OSV
RUSTSEC-2026-0278 · OSV
UBUNTU-CVE-2026-78422 · OSV
CVE-2026-78422 · OSV
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