How severe is CVE-2026-9780?

CVE-2026-9780 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-9780 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (48th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-9780?

CVE-2026-9780 affects Quest Netvault Backup. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-9780?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-9780 have an EU (EUVD) identifier?

Yes. CVE-2026-9780 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-39140.

When was CVE-2026-9780 published?

CVE-2026-9780 was published on 2026-06-25 and last updated on 2026-06-26.

CVE-2026-9780

CVE-2026-9780 is a high-severity vulnerability in Quest Netvault Backup with a CVSS 3.x base score of 8.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.

Key facts

Severity: High (CVSS 3.x base score 8.8)
EPSS exploit prediction: 1% (48th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-39140
Weakness: CWE-79
Affected product: Quest Netvault Backup
Published: 2026-06-25
Last modified: 2026-06-26

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.

Frequently asked questions

What is 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.
How severe is CVE-2026-9780?: CVE-2026-9780 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-9780 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (48th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-9780?: CVE-2026-9780 affects Quest Netvault Backup. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-9780?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-9780 have an EU (EUVD) identifier?: Yes. CVE-2026-9780 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-39140.
When was CVE-2026-9780 published?: CVE-2026-9780 was published on 2026-06-25 and last updated on 2026-06-26.

References

Affected products (1)

cpe:2.3:a:quest:netvault_backup:*:*:*:*:*:*:*:*

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