nextcloud server Cross-Site Scripting Vulnerability

CVE Details

• Protection status: Protected by Atomicorp rules · About protection statuses
• CVE: CVE-2025-59788
• Name: nextcloud server Cross-Site Scripting Vulnerability
• Severity: Medium
• CVSS: 5.4 (v3.1) (Medium)
• CVSS version: 3.1
• CVSS source: NVD
• CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
  • Attack vector: Network
  • Attack complexity: Low
  • Privileges required: Low
  • User interaction: Required
  • Scope: Changed
  • Confidentiality impact: Low
  • Integrity impact: Low
  • Availability impact: None
• CWE: CWE-79 — Improper Neutralization of Input During Web Page Generation (‘Cross-site Scripting’), CWE-749 — Exposed Dangerous Method or Function
• Related CAPEC attack patterns (via MITRE CWE relationships): CAPEC-209 (opens in a new tab) , CAPEC-500 (opens in a new tab) , CAPEC-588 (opens in a new tab) , CAPEC-591 (opens in a new tab) , CAPEC-592 (opens in a new tab) , CAPEC-63 (opens in a new tab) , CAPEC-85 (opens in a new tab)
• Vendor: nextcloud
• Vulnerable product: nextcloud server
• CVE published: 2025-12-04
• CVE last modified: 2026-10-18
• Affected versions (NVD configurations):
  • nextcloud server: >= 30.0.0, < 30.0.17
  • nextcloud server: >= 31.0.0, < 31.0.10
  • nextcloud server: >= 32.0.0, < 32.0.1
  • nextcloud server: >= 22.0.0, < 22.2.10.33
  • nextcloud server: >= 23.0.0, < 23.0.12.29
  • nextcloud server: >= 24.0.0, < 24.0.12.28
  • nextcloud server: >= 25.0.0, < 25.0.13.23
  • nextcloud server: >= 26.0.0, < 26.0.13.20
  • nextcloud server: >= 27.0.0, < 27.1.11.20
  • nextcloud server: >= 28.0.0, < 28.0.14.11
  • nextcloud server: >= 29.0.0, < 29.0.16.8
• EPSS: 0.0030; 21.7th percentile as of 2026-10-21 (FIRST (opens in a new tab) )
• Latest Update: 2026-10-19
• Selected Rule IDs observed: 333140 , 333141 , 340099 , 340147 , 340148 , 341099 , 341256 , 341266 , 342259 , 346755 , 350147 , 350148
• Matching rules: 12; rules with blocking actions: 12
• Would-block Rule IDs: 333140 , 333141 , 340099 , 340147 , 340148 , 341099 , 341256 , 341266 , 342259 , 346755 , 350147 , 350148
• Request surfaces inspected: JSON request data, Request URI, Request argument names, Request arguments, Request cookies, Request filename, Request headers, SOAP request data, XML request data

Vulnerability Description

Cross-site scripting (XSS) vulnerability in a reachable files_pdfviewer example directory in Nextcloud with versions before 22.2.10.33, 23.0.12.29, 24.0.12.28, 25.0.13.23, 26.0.13.20, 27.1.11.20, 28.0.14.11, 29.0.16.8, 30.0.17, 31.0.10, and 32.0.1 allows attackers to execute arbitrary JavaScript in the context of a user’s browser via a crafted PDF file to viewer.html. This issue is related to CVE-2024-4367, but the root cause of this Nextcloud issue is that the product exposes executable example code on a same-origin basis.

Recommended Actions

1. Maintain the observed Atomicorp protections. Keep your Atomicorp commercial rules current and confirm that the selected observed rules (333140 , 333141 , 340099 , 340147 , 340148 , 341099 , 341256 , 341266 , 342259 , 346755 , 350147 , 350148 ) have not been locally disabled. Atomicorp commercial rules are enabled by default. If you use Atomic WAF, review the applicable policy and rule settings.

2. Apply the vendor’s remediation. WAF protection is defense in depth and does not replace upgrading or following the affected vendor’s guidance.

   • Affected versions: Nextcloud versions earlier than 22.2.10.33.
   • Affected versions: Nextcloud versions earlier than 23.0.12.29.
   • Affected versions: Nextcloud versions earlier than 24.0.12.28.
   • Affected versions: Nextcloud versions earlier than 25.0.13.23.
   • Affected versions: Nextcloud versions earlier than 26.0.13.20.
   • Affected versions: Nextcloud versions earlier than 27.1.11.20.
   • Affected versions: Nextcloud versions earlier than 28.0.14.11.
   • Affected versions: Nextcloud versions earlier than 29.0.16.8.
   • Affected versions: Nextcloud versions earlier than 30.0.17.
   • Affected versions: Nextcloud versions earlier than 31.0.10.
   • Affected versions: Nextcloud versions earlier than 32.0.1.
   • Recommended upgrade: Upgrade Nextcloud to 22.2.10.33 or later.
   • Recommended upgrade: Upgrade Nextcloud to 23.0.12.29 or later.
   • Recommended upgrade: Upgrade Nextcloud to 24.0.12.28 or later.
   • Recommended upgrade: Upgrade Nextcloud to 25.0.13.23 or later.
   • Recommended upgrade: Upgrade Nextcloud to 26.0.13.20 or later.
   • Recommended upgrade: Upgrade Nextcloud to 27.1.11.20 or later.
   • Recommended upgrade: Upgrade Nextcloud to 28.0.14.11 or later.
   • Recommended upgrade: Upgrade Nextcloud to 29.0.16.8 or later.
   • Recommended upgrade: Upgrade Nextcloud to 30.0.17 or later.
   • Recommended upgrade: Upgrade Nextcloud to 31.0.10 or later.
   • Recommended upgrade: Upgrade Nextcloud to 32.0.1 or later.
   • The CVE record does not include written upgrade or workaround instructions, but it does publish the following patch or mitigation reference:
     • Patch or mitigation information (opens in a new tab)

3. Validate after changes. Confirm rule updates are current, review WAF events for the affected application, and test application behavior after vendor upgrades, mitigations, or local policy changes.

Research Notes

Atomicorp WAF protections are designed around attack techniques and exploit behaviors, allowing existing protections to apply across multiple vulnerabilities without requiring a unique rule for every CVE.

Public Vulnerability References

• NVD (opens in a new tab)
• CVE Record (opens in a new tab)
• Vendor advisory: https://github.com/nextcloud/security-advisories/security/advisories/GHSA-24wp-p865-7j4r (opens in a new tab)
• CVE authority reference: https://nextcloud.com (opens in a new tab)
• Exploit or technical research: https://www.redteam-pentesting.de/en/advisories/rt-sa-2025-003/ (opens in a new tab)

Test or Research Source

• Source: Atomicorp AI Research Framework
• Tags: cve, derived, waf-probe, xss

Research Note Context

This research note documents exploit-technique analysis associated with this vulnerability and references Atomicorp WAF protections observed during engineering review, testing, or validation activities.

Atomicorp security controls are generally designed to identify and mitigate attack techniques and exploit behaviors rather than individual CVE identifiers. As a result, protections developed for one vulnerability may also apply to related attack variants and future vulnerabilities using similar techniques.

Learn More

Atomicorp develops commercially supported security technologies for web applications, servers, endpoints, workloads, and legacy enterprise platforms.

Organizations interested in protecting systems against exploit techniques associated with vulnerabilities such as this one can learn more about:

• Atomic ModSecurity Rules: commercially maintained WAF rules for ModSecurity deployments, including protections for web attacks, bots, scanners, malware, exploitation attempts, and emerging vulnerability classes.
• Atomic WAF: an enterprise web application firewall with Atomicorp rules, centralized management, reporting, authentication controls, and operational tooling.
• Atomic ModSecurity Integrator: a special licensing option for MSPs, MSSPs, OEMs, VARs, reverse proxy providers, and other integrators who want to incorporate Atomicorp ModSecurity rule technology into their own products or services.
• Atomic OSSEC: an enterprise OSSEC-based intrusion detection, compliance, and security monitoring platform.
• Atomic Protector: workload protection for Linux, web, cloud, data center, and hybrid environments.

For additional information, product evaluations, or technical discussions, visit https://www.atomicorp.com/ or https://modsecurity.io/ (opens in a new tab) .