# 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.

- **Severity:** High 7.3 (`CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **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:** Yes
- **Published:** 31 Aug 2026
- **Updated:** 1 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-78422, GHSA-j48v-cvqq-xcv6, RUSTSEC-2026-0278, UBUNTU-CVE-2026-78422

## 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.

Weakness: CWE-686 (Function Call With Incorrect Argument Type), CWE-367 (Time-of-check Time-of-use (TOCTOU) Race Condition)

## Which versions are affected by CVE-2026-78422?

1 open source package ship an affected version, including zbus_polkit.


| Package | Ecosystem | 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-78422 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-78422 in the wild and no public exploit code.

Affected packages and fixed versions:
- zbus_polkit (crates.io): affected from 0.0.0-0; fixed in 5.1.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-78422/ (Markdown: https://insights.sbomify.com/CVE-2026-78422/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-78422
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-78422
- OSV: https://osv.dev/vulnerability/CVE-2026-78422

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-78422/
Summaries are generated and may contain mistakes; the official description above is the record.