CVE-2026-9780 Quest NetVault Backup addclient3 Cross-Site Scripting Authentication Bypass Vulnerability

High 8.8 Published 24 Jun 2026 Updated 25 Jun 2026

Remote attackers can bypass authentication via XSS in Quest NetVault Backup, potentially leading to arbitrary code execution as SYSTEM.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: A user has to click or open something
Fix: None listed

What is CVE-2026-9780?

CVE-2026-9780 is a high-severity cross-site scripting vulnerability in Quest NetVault Backup, published on 24 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official description

Quest NetVault Backup addclient3 Cross-Site Scripting Authentication Bypass Vulnerability. This vulnerability allows remote attackers to bypass authentication on affected installations of Quest NetVault Backup. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file.

The specific flaw exists within the addclient3 webpage. The issue results from the lack of proper validation of user-supplied data, which can lead to the injection of an arbitrary script. An attacker can leverage this in conjunction with other vulnerabilities to execute arbitrary code in the context of SYSTEM. Was ZDI-CAN-27666.

Weakness: CWE-79

Which versions are affected by CVE-2026-9780?

It affects 1 product.

Products include Quest Netvault Backup.

How do I fix CVE-2026-9780?

No fix has been published for CVE-2026-9780 yet. Limit exposure of the affected software until one is available.

Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.

Is CVE-2026-9780 being exploited?

There is no known exploitation of CVE-2026-9780 in the wild and no public exploit code.

Sources

Also known as GHSA-rhv6-pj5x-4qfc.