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CVE-2025-66514

Nextcloud Mail stored HTML injection in subject text

Published: Dec 5, 2025Updated: Dec 9, 2025 Sources: CVE List NVD BDUCWE-79
3.5LOW
NVD MITRE
EPSS Score
0.2%
Top 84.3%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available
Self-Check
Not available

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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:LUI:RS:UC:NI:LA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:LPrivileges Required
Low
UI:RUser Interaction
Required
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:LIntegrity
Low
A:NAvailability
None
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Weaknesses

CWE-79

Affected Products

nextcloud
oss-project·DEaka nextcloud server
mailSaaSSaaS Service
Cloud & SaaS / saas-application
security-advisoriesSaaSSaaS Service
Cloud & SaaS / saas-application
ООО «Ред Софт»
commercial·RUaka red soft
РЕД ОСOn-premOS
Operating Systems / linux-distro
Nextcloud GmbH
commercial·DEaka nextcloud server, nextcloud enterprise server, nextcloud calendar
Nextcloud mailSaaSSaaS Service
Cloud & SaaS / saas-application

Exploitability

Official Patch Available

Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

2 techniques
Execution
Initial Access
View detailed technique mapping

References

https://github.com/nextcloud/mail/commit/c64fcc3b79e0c089b5e1d2e04a07bfa740b2ac09
github.com
https://github.com/nextcloud/mail/pull/11740
github.com
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-v394-8gpc-6fv5
github.com
and 7 more references View all →

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