CVE-2025-66514

Nextcloud Mail stored HTML injection in subject text

CVSS 3.5 LOWEPSS 0.2%CWE-79

Vexday Risk Score

8Low

SSVC decision (CISA)

Track

No exploitation signal → monitor

CVSS 3.5EPSS 0.2%KEV nãoPoC —Nuclei —Metasploit —Patch —

Lifecycle

05 Dec 2025Published on NVD

Recommendation: Monitor — no exploitation signal at the moment.

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.

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N

Affected products

nextcloud · security-advisories

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References

https://github.com/nextcloud/mail/commit/c64fcc3b79e0c089b5e1d2e04a07bfa740b2ac09 https://github.com/nextcloud/mail/pull/11740 https://github.com/nextcloud/security-advisories/security/advisories/GHSA-v394-8gpc-6fv5 https://hackerone.com/reports/3357036