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CVE-2025-66514

18
FAUCET Score

CVE-2025-66514 describes a stored HTML injection vulnerability in Nextcloud Mail versions prior to 5.5.3, allowing an authenticated user to inject HTML into email subjects. This medium-severity vulnerability (CVSS 5.4) requires user interaction and a low-privileged account, potentially leading to limited impact on confidentiality and integrity. There is currently no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 5.5.3CPE matchmatch criteria
cpe:2.3:a:nextcloud:mail:*:*:*:*:*:nextcloud:*:*

CVSS Data

CVSS version used by this source: 3.1

3.5LOW

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
2.1
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.22%
Probability of exploitation in next 30 days
EPSS Percentile
12.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0022 is in the 14th percentile among its peer group of 15,224 CVEs.

Social Chatter

No social media mentions found for this CVE.

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.0 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

github_advisorypatch availablevia nvd_reference
View patch

References

github.com / nextcloud/mail/commit/c64fcc3b79e0c089b5e1d2e04a07bfa740b2ac09
Patch
github.com / nextcloud/mail/pull/11740
Issue TrackingPatch
github.com / nextcloud/security-advisories/security/advisories/GHSA-v394-8gpc-6fv5
PatchVendor Advisory
hackerone.com / reports/3357036
Permissions RequiredVendor Advisory