# CVE-2026-37503: V2Board stored XSS in theme configuration custom_html

Source: https://junglewise.ai/threats/cve-2026-37503-v2board-stored-xss-in-theme-configuration-custom-html  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-01. Updated: 2026-05-11  
License: CC BY 4.0 with a link back

CVE-2026-37503 · Severity: medium · CVSS 6.9 · Published 2026-05-01

V2Board is a management panel used for proxy protocol services. A security vulnerability exists where an administrator can inject malicious scripts into the dashboard's theme configuration. If exploited, these scripts will run in the browsers of all site visitors, potentially allowing the attacker to steal login sessions, hijack accounts, or perform phishing attacks against users.

Technologies: [V2board](https://junglewise.ai/threats/technologies/v2board). Vendors: [V2board](https://junglewise.ai/threats/vendors/v2board).

## Quick answers

**Is CVE-2026-37503 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-37503 being exploited in the wild.

**How severe is CVE-2026-37503?** Medium severity, with a CVSS score of 6.9, published 1 May 2026.

**Which products and versions are affected?** V2Board V2Board up to and including 1.7.4.

**Is there a fix for CVE-2026-37503?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-37503 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-37503?** Check whether you run V2board. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A stored Cross-Site Scripting (XSS) vulnerability exists in V2Board versions up to and including 1.7.4. The root cause is the use of unescaped Blade interpolation ({!! !!}) for the 'custom_html' field within the dashboard.blade.php template. An attacker with administrative privileges can use the saveThemeConfig API to inject arbitrary JavaScript. Because the payload is rendered on the dashboard, it executes in the context of any user (including other admins and site visitors) who views the page. This can lead to session hijacking via cookie theft or unauthorized actions performed on behalf of the victim. The project is reportedly unmaintained, and no official patch is available; users are advised to manually switch to escaped output ({{ }}) in the affected Blade template.

## Affected products

- V2Board V2Board up to and including 1.7.4

## Timeline

- 2026-04-30: disclosed: Vulnerability reported by Innora Security Research
- 2026-05-01: advisory: CVE-2026-37503 published

## References

- [https://gist.github.com/sgInnora/1330e1a82caa79906eec55eeff2c99b9](https://gist.github.com/sgInnora/1330e1a82caa79906eec55eeff2c99b9)
- [https://github.com/v2board/v2board](https://github.com/v2board/v2board)

## Related threats

- [V2Board SQL injection in Admin UserController](https://junglewise.ai/threats/cve-2026-37505-v2board-sql-injection-in-admin-usercontroller)
- [V2Board sensitive token exposure in UniProxyController](https://junglewise.ai/threats/cve-2026-37504-v2board-sensitive-token-exposure-in-uniproxycontroller)
- [V2Board and Xboard authentication token exposure in loginWithMailLink](https://junglewise.ai/threats/cve-2026-39912-v2board-and-xboard-authentication-token-exposure-in)