Nextcloud Mail <5.5.3: Stored HTML Injection in Message List
CVE-2025-66514 Published on December 5, 2025
Nextcloud Mail stored HTML injection in subject text
Nextcloud Mail is the mail app for Nextcloud, a self-hosted productivity platform. Prior to 5.5.3, a stored HTML injection in the Mail app's message list allowed an authenticated user to inject HTML into the email subjects. Javascript was correctly blocked by the content security policy of the Nextcloud Server code.
Vulnerability Analysis
CVE-2025-66514 is exploitable with network access, requires user interaction and a small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality, with no impact on integrity, and no impact on availability.
Weakness Type
What is a XSS Vulnerability?
The software does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
CVE-2025-66514 has been classified to as a XSS vulnerability or weakness.
Products Associated with CVE-2025-66514
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Affected Versions
nextcloud security-advisories Version >= 5.2.0-beta.1, < 5.5.3 is affected by CVE-2025-66514Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.