Description
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.
References (4)
Core 4
Core References
Patch, Vendor Advisory x_refsource_confirm
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-v394-8gpc-6fv5
Issue Tracking, Patch x_refsource_misc
https://github.com/nextcloud/mail/pull/11740
Patch x_refsource_misc
https://github.com/nextcloud/mail/commit/c64fcc3b79e0c089b5e1d2e04a07bfa740b2ac09
Permissions Required, Vendor Advisory x_refsource_misc
https://hackerone.com/reports/3357036
Scores
CVSS v3
3.5
EPSS
0.0001
EPSS Percentile
1.9%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
CISA SSVC
Vulnrichment
Exploitation
none
Automatable
no
Technical Impact
partial
Details
CWE
CWE-79
Status
published
Products (1)
nextcloud/mail
< 5.5.3
Published
Dec 05, 2025
Tracked Since
Feb 18, 2026