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Netvault BackupApplication · Quest

CVE-2026-9780

HIGH · 8.8 CVSS v3.0 Published 2026-06-25
Fix available
A fix is available. Upgrade to 14.0.2 or later.
See remediation →
95/100
Remediation priority · Urgent
Remotely reachable No privileges 8 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

This is a cross-site scripting (XSS) vulnerability in Quest NetVault Backup's addclient3 webpage that allows attackers to inject arbitrary scripts through unsanitized user input. While described as an authentication bypass, the requirement for user interaction (victim visiting a malicious page) suggests the primary vector is reflective or stored XSS that can be chained with other vulnerabilities to achieve SYSTEM-level code execution.

MitigationApply vendor patch when available; implement input validation and output encoding on the addclient3 webpage; consider web application firewall rules as an interim control.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Netvault BackupApplication
Affected:< 14.0.2

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Confirm Quest NetVault Backup is installed
    Locate NetVault Backup installation directory or check installed programs on the server. Typical paths may include C:\Program Files\Quest\NetVault Backup or /opt/netvault.
    Affected if Quest NetVault Backup software is present on the system
  2. Determine the installed version of NetVault Backup
    Check the version of NetVault Backup installed. This is typically available through the NetVault Backup web interface (usually port 8443 or 20080) or via the installed programs list in the operating system.
    Affected if The installed version is any version prior to 14.0.2 (e.g., 14.0, 13.x, 12.x, or earlier)
  3. Verify the addclient3 web page is accessible
    Access the NetVault Backup web interface and navigate to the addclient3 page, or attempt to access it directly via URL (typically https://server:8443/cgi-bin/nvwebacc.exe?func=addclient3 or similar path).
    Affected if The addclient3 web page loads and accepts user input without visible sanitization indicators
  4. Check if the web interface is exposed to untrusted networks
    Review network configuration to determine if the NetVault Backup web interface (port 8443 or 20080) is bound to external interfaces or accessible from untrusted networks rather than only localhost or internal management networks.
    Affected if The web interface is accessible from untrusted networks or the internet

You are affected if Quest NetVault Backup is installed with a version lower than 14.0.2 and the addclient3 web page is accessible, particularly from untrusted networks.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 14.0.2 or later
Fixed in 14.0.2
Interim mitigation

Apply vendor patch when available; implement input validation and output encoding on the addclient3 webpage; consider web application firewall rules as an interim control.

Recommended fix Moderate confidence

NetVault Backup 14.0.2 or later

  1. 1. Back up the current NetVault Backup configuration and database before performing any upgrade.
  2. 2. Download NetVault Backup version 14.0.2 or later from the Quest Support portal (support.quest.com).
  3. 3. Stop the NetVault Backup service on the server.
  4. 4. Install the NetVault Backup 14.0.2 upgrade following the standard upgrade procedure documented by Quest.
  5. 5. After installation, verify the service starts successfully and the web interface is accessible.
  6. 6. Confirm the addclient3 page is functioning correctly and the vulnerability is no longer present.
Caveat Review Quest release notes for 14.0.2 for any configuration changes or deprecated features before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Netvault Backup Scoped from the published advisory
  • Consultation3.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
17.0 hours of engineering $3,000
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-9780 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data