# CVE-2026-9780: Quest NetVault Backup XSS authentication bypass in addclient3

Source: https://junglewise.ai/threats/cve-2026-9780-quest-netvault-backup-xss-authentication-bypass-in-addclient3  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-25. Updated: 2026-06-25  
License: CC BY 4.0 with a link back

CVE-2026-9780 · Severity: high · CVSS 8.8 · Published 2026-06-25

Quest NetVault Backup, a data protection and recovery solution, contains a security flaw in its web management interface. A remote attacker could trick a user into visiting a malicious link, allowing the attacker to bypass authentication and gain unauthorized access to the system. If combined with other flaws, this could allow an attacker to take full control of the backup server and its data.

Technologies: [Quest NetVault Backup](https://junglewise.ai/threats/technologies/netvault-backup). Vendors: [Quest](https://junglewise.ai/threats/vendors/quest).

## Quick answers

**Is CVE-2026-9780 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-9780 being exploited in the wild.

**How severe is CVE-2026-9780?** High severity, with a CVSS score of 8.8, published 25 June 2026.

**Which products and versions are affected?** Quest NetVault Backup 14.0.1.7.

**Is there a fix for CVE-2026-9780?** A patch was published on 2026-06-24: Vendor released version 14.0.2 to address the issue Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-9780 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-9780?** Check whether you run Quest NetVault Backup 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 Cross-Site Scripting (XSS) vulnerability exists within the 'addclient3' webpage of Quest NetVault Backup due to insufficient validation of user-supplied data. A remote, unauthenticated attacker can exploit this by inducing a user to visit a specially crafted URL or open a malicious file, leading to arbitrary script execution in the victim's browser session. This flaw specifically enables an authentication bypass. According to the advisory, this vulnerability can be chained with other issues to achieve arbitrary code execution with SYSTEM privileges. The issue is resolved in version 14.0.2.

## Affected products

- Quest NetVault Backup 14.0.1.7

## Timeline

- 2025-09-24: disclosed: Vulnerability reported to vendor via ZDI
- 2026-06-24: patched: Vendor released version 14.0.2 to address the issue
- 2026-06-24: advisory: Coordinated public release of advisory

## References

- [https://support.quest.com/technical-documents/netvault/14.0.2/release-notes](https://support.quest.com/technical-documents/netvault/14.0.2/release-notes)
- [https://www.zerodayinitiative.com/advisories/ZDI-26-369/](https://www.zerodayinitiative.com/advisories/ZDI-26-369/)

## Related threats

- [Quest NetVault Backup nvpmgr integer underflow denial-of-service](https://junglewise.ai/threats/cve-2026-13270-quest-netvault-backup-nvpmgr-integer-underflow-denial-of-service)
- [Quest NetVault Backup numeric truncation error denial of service](https://junglewise.ai/threats/cve-2026-13269-quest-netvault-backup-stnzcreatekey-numeric-truncation-error)
- [Quest NetVault Backup command injection in NVBULogDaemon](https://junglewise.ai/threats/cve-2026-9787-quest-netvault-backup-command-injection-in-nvbulogdaemon)
- [Quest NetVault Backup SQL injection in NVBUDashboard](https://junglewise.ai/threats/cve-2026-9786-quest-netvault-backup-sql-injection-in-nvbudashboard)
- [Quest NetVault Backup SQL injection in NVBULibrarySlot](https://junglewise.ai/threats/cve-2026-9785-quest-netvault-backup-sql-injection-in-nvbulibraryslot)