What’s Vulnerable › Vulnerabilities

CVE-2021-22878

• Severity: medium (CVSS 4.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.1% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-03-03 · updated 2026-06-17
• Weakness: CWE-79

Description

Nextcloud Server prior to 20.0.6 is vulnerable to reflected cross-site scripting (XSS) due to lack of sanitization in `OC.Notification.show`.

Affected products

• Fedoraproject Fedora: 34
• Nextcloud Server: before 20.0.6 — fixed in 20.0.6

How to fix

Upgrade to a fixed version: Nextcloud Server 20.0.6. Check the vendor advisory for mitigations.

References

• https://github.com/nextcloud/server/pull/25234
• https://hackerone.com/reports/896522
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L6BO6P6MP2MOWA6PZRXX32PLWPXN5O4S/
• https://nextcloud.com/security/advisory/?id=NC-SA-2021-005
• https://github.com/nextcloud/server/pull/25234
• https://hackerone.com/reports/896522
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L6BO6P6MP2MOWA6PZRXX32PLWPXN5O4S/
• https://nextcloud.com/security/advisory/?id=NC-SA-2021-005

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