# CVE-2026-55426: linuxfabrik-lib: Local privilege escalation using embedded command

> Attackers can inject commands via monitoring plugin arguments to execute code as root, requiring an upgrade to linuxfabrik-lib and plugins.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 18 Aug 2026
- **Updated:** 20 Aug 2026
- **Also known as:** GHSA-798h-hpph-m24j, PYSEC-2026-2594

## What is CVE-2026-55426?

CVE-2026-55426 is a high-severity command injection vulnerability in Linuxfabrik lib, published on 18 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

linuxfabrik-lib provides Python modules for database access, caching, shell execution, and API integrations, and Linuxfabrik Monitoring Plugins uses those modules to run external monitoring commands. From the earliest affected releases until linuxfabrik-lib 5.0.0 and Linuxfabrik Monitoring Plugins 6.0.0, check plugins embedded user-controlled values in command strings passed to lib.shell.shell_exec(), which split strings at pipe characters and executed the resulting commands. In check-plugins/restic-check/restic-check, the --repo parameter could inject a pipe-delimited command into a constructed restic invocation, and sudo-authorized execution allowed a compromised nagios or icinga account to run that command as root. The shared library also accepted command strings and a shell parameter, while numerous plugins constructed external commands from attacker-influenced arguments. The fixes require argv lists, always use shell=False, remove pipe splitting, and reject option-like positional values through lib.shell.safe_cli_value(). These issues are fixed in linuxfabrik-lib 5.0.0 and Linuxfabrik Monitoring Plugins 6.0.0.

Weakness: CWE-78 (Improper Neutralization of Special Elements used in an OS Command)

## Which versions are affected by CVE-2026-55426?

3 open source packages ship an affected version, including linuxfabrik-lib.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `linuxfabrik-lib` | PyPI | All versions | 5.0.0 |
| `linuxfabrik-lib` | PyPI | All versions | 5.0.0 |
| `linuxfabrik-lib` | PyPI | All versions | 5.0.0 |

## How do I fix CVE-2026-55426?

Upgrade linuxfabrik-lib to 5.0.0 or later.

## Is CVE-2026-55426 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55426 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55426 and fix it if it is affected.

What it is: CVE-2026-55426 is a high-severity command injection vulnerability in Linuxfabrik lib, published on 18 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55426 exists.

Affected packages and fixed versions:
- linuxfabrik-lib (PyPI): affected all versions; fixed in 5.0.0
- linuxfabrik-lib (PyPI): affected all versions; fixed in 5.0.0
- linuxfabrik-lib (PyPI): affected all versions; fixed in 5.0.0

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-2026-55426/ (Markdown: https://insights.sbomify.com/CVE-2026-55426/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55426
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55426
- OSV: https://osv.dev/vulnerability/CVE-2026-55426

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-55426/
Summaries are generated and may contain mistakes; the official description above is the record.