# CVE-2026-12503: Loytec LINX firmware: Improper Link Resolution in /usr/bin/larm_starter

> An authenticated attacker can escalate privileges to root via a symlink attack in the larm_starter binary on Loytec LINX devices.

- **Severity:** Critical 9.2 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:H/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 24 Jul 2026
- **Updated:** 24 Jul 2026
- **Also known as:** GHSA-4p7f-6rpf-28mq

## What is CVE-2026-12503?

CVE-2026-12503 is a critical path traversal vulnerability in Loytec L-DALI, published on 24 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Improper Link Resolution (CWE-59) in `/usr/bin/larm_starter` in Loytec L-INX, L-GATE, L-ROC, L-IOB, L-DALI, L-VIS and L-PAD through 8.4.16 on LINX-A64 allows an authenticated `larmapp` attacker to make `/etc/passwd` writable by the `larmapp` group (leading to root privilege escalation) via a symlink attack on `/etc/lighttpd/ssl/server.pem`.

Weakness: CWE-59 (Improper Link Resolution Before File Access)

## Which versions are affected by CVE-2026-12503?


## How do I fix CVE-2026-12503?

No fix has been published for CVE-2026-12503 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-12503 being exploited?

There is no known exploitation of CVE-2026-12503 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-12503 and fix it if it is affected.

What it is: CVE-2026-12503 is a critical path traversal vulnerability in Loytec L-DALI, published on 24 Jul 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-2026-12503 in the wild and no public exploit code.

Affected product: Loytec L-DALI. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-12503/ (Markdown: https://insights.sbomify.com/CVE-2026-12503/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-12503
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-12503
- OSV: https://osv.dev/vulnerability/CVE-2026-12503

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-12503/
Summaries are generated and may contain mistakes; the official description above is the record.