# CVE-2026-103540: formtools.org Form Tools Client Settings Clients.class.php updateClientSettingsTab special elements in template engine

> Remote attackers can execute arbitrary code via template injection in Form Tools client settings, requiring authentication.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 1 Oct 2026
- **Updated:** 1 Oct 2026
- **Also known as:** GHSA-r99g-f87j-9mpc

## What is CVE-2026-103540?

CVE-2026-103540 is a medium-severity code injection vulnerability in formtools.org Form Tools, published on 1 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A security vulnerability has been detected in formtools.org Form Tools up to 3.1.1. This vulnerability affects the function Clients::updateClientSettingsTab of the file global/code/Clients.class.php of the component Client Settings. The manipulation of the argument page_titles leads to improper neutralization of special elements used in a template engine. It is possible to initiate the attack remotely. The exploit has been disclosed publicly and may be used. The project was informed of the problem early through an issue report but has not responded yet.

Weakness: CWE-791 (Incomplete Filtering of Special Elements), CWE-1336 (Improper Neutralization of Special Elements Used in a Template Engine)

## Which versions are affected by CVE-2026-103540?


## How do I fix CVE-2026-103540?

No fix has been published for CVE-2026-103540 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-103540 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-103540 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-103540 and fix it if it is affected.

What it is: CVE-2026-103540 is a medium-severity code injection vulnerability in formtools.org Form Tools, published on 1 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-103540 exists.

Affected product: formtools.org Form Tools. 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-2026-103540/ (Markdown: https://insights.sbomify.com/CVE-2026-103540/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-103540
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-103540
- OSV: https://osv.dev/vulnerability/CVE-2026-103540

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-103540/
Summaries are generated and may contain mistakes; the official description above is the record.