XSS in Quest Netvault Backup
CVE-2026-9780
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.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.8 (High). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.009 (59.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 59th percentile — 59.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.009 · newest: 0.009 · change: 0.000
Affected products
- Quest Netvault Backup — versions 14.0.1.7
- Quest Netvault Backup
Weakness classification (CWE)
References
- www.zerodayinitiative.com/advisories/ZDI-26-369/ (x_research-advisory, Vendor Advisory)
- support.quest.com/technical-documents/netvault/14.0.2/release-notes (vendor-advisory, Release Notes)
Frequently asked questions
- What is CVE-2026-9780?
- CVE-2026-9780 is a high-severity vulnerability in Quest Netvault Backup, classified under Cross-site Scripting. CVSS score: 8.8/10. Published 2026-06-25.
- How severe is CVE-2026-9780?
- High severity. CVSS v3 base score is 8.8 out of 10.