CVE-2026-9780VulnerabilityPublished 24 Jun 2026

ZDI-26-369: Quest NetVault Backup addclient3 Cross-Site Scripting Authentication Bypass Vulnerability

Source Zero Day Initiative

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Not known to be exploited.

Data as of 5 Nov 2026, 23:24 UTC

Severity

High

Rated High by Threat Radar from the Zero Day Initiative text · No CVSS score from NVD or the CNA

EPSS: 0.9% chance of exploitation in 30 days – higher than 60% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

Exploitation evidence

Disclosed: evidence found.
Public on cve.org; its publication date is not in this record
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

remote

What to do

AI-suggested

Quest has issued an official update to correct this vulnerability. Applying the vendor's update is the recommended remediation. No additional mitigation steps are specified or required beyond installing the official fix.

Description

CVE-2026-9780 is a vulnerability in Quest NetVault Backup's addclient3 webpage that allows remote attackers to bypass authentication by injecting arbitrary scripts due to improper validation of user-supplied data. Exploitation requires user interaction, such as visiting a malicious page or opening a malicious file. The vulnerability can be leveraged with other flaws to execute arbitrary code with SYSTEM privileges. Quest has issued an update to address this issue.

Impact

Successful exploitation allows remote attackers to bypass authentication and potentially execute arbitrary code with SYSTEM privileges on affected Quest NetVault Backup installations. This compromises confidentiality, integrity, and availability of the system.

Summary

This vulnerability in Quest NetVault Backup affects the addclient3 webpage, where insufficient validation of user input allows injection of arbitrary scripts. This flaw enables remote attackers to bypass authentication if the target interacts with malicious content. The vulnerability has a CVSS rating of 8.8 assigned by ZDI and can lead to full system compromise when combined with other vulnerabilities. Quest has released an update to fix this issue.

References

zerodayinitiative.com/advisories/ZDI-26-369/ (opens in a new tab)

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