# CVE-2026-34803: Endian Firewall stored XSS in QoS classes management interface

Source: https://junglewise.ai/threats/cve-2026-34803-endian-firewall-stored-xss-in-qos-classes-management-interface  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-02. Updated: 2026-07-24  
License: CC BY 4.0 with a link back

CVE-2026-34803 · Severity: medium · CVSS 6.4 · Published 2026-04-02

Endian Firewall, a security appliance used to protect corporate and community networks, contains a vulnerability in its Quality of Service (QoS) management interface. An authorized user with low-level access can inject malicious scripts into the system's configuration. These scripts are then executed in the browsers of other administrators when they view the affected management page, potentially leading to unauthorized actions or the theft of sensitive session information.

Technologies: [Endian Firewall Community](https://junglewise.ai/threats/technologies/firewall-community). Vendors: [Endian](https://junglewise.ai/threats/vendors/endian).

## Quick answers

**Is CVE-2026-34803 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-34803 being exploited in the wild.

**How severe is CVE-2026-34803?** Medium severity, with a CVSS score of 6.4, published 2 April 2026.

**Which products and versions are affected?** Endian Firewall Community up to and including 3.3.25.

**Is there a fix for CVE-2026-34803?** 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-2026-34803 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-34803?** Check whether you run Endian Firewall Community at an affected version. 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 Endian Firewall version 3.3.25 and earlier. The flaw is located in the '/manage/qos/classes/' endpoint, where the 'name' parameter fails to properly neutralize user-supplied input before it is stored and subsequently rendered in the web interface. An authenticated attacker with network access to the management console can submit a malicious payload that will execute arbitrary JavaScript in the context of any user (such as an administrator) who later navigates to the QoS classes page. This can lead to session hijacking or unauthorized configuration changes. The vulnerability is tracked as CWE-79.

## Affected products

- Endian Firewall Community up to and including 3.3.25

## Timeline

- 2026-04-02: disclosed
- 2026-04-02: advisory

## References

- [https://help.endian.com/hc/en-us/sections/360004371358-Community](https://help.endian.com/hc/en-us/sections/360004371358-Community)
- [https://www.vulncheck.com/advisories/endian-firewall-manage-qos-classes-name-stored-cross-site-scripting](https://www.vulncheck.com/advisories/endian-firewall-manage-qos-classes-name-stored-cross-site-scripting)

## Related threats

- [Endian Firewall stored XSS in remark parameter](https://junglewise.ai/threats/cve-2026-34823-endian-firewall-stored-xss-in-remark-parameter)
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- [Endian Firewall stored XSS in openvpnclient.cgi](https://junglewise.ai/threats/cve-2026-34819-endian-firewall-stored-xss-in-openvpnclient-cgi)