PT-2025-49300 · Nextcloud+1 · Nextcloud Contacts+1

Published 2025-12-05 · Updated 2026-01-29 · CVE-2025-66554

Positive Technologies (AI Summary)

CVSS v2.0

5.5

Medium

Base vector

AV:N/AC:L/Au:S/C:P/I:P/A:N

Name of the Vulnerable Software and Affected Versions Nextcloud Contacts app versions prior to 5.5.4 Nextcloud Contacts app versions prior to 6.0.6 Nextcloud Contacts app versions prior to 7.2.5

Description A malicious user could modify the organisation and title fields to load additional CSS files. Javascript and other options were blocked by the content security policy of the Nextcloud Server code.

Recommendations Update to Nextcloud Contacts app version 5.5.4 or later. Update to Nextcloud Contacts app version 6.0.6 or later. Update to Nextcloud Contacts app version 7.2.5 or later.

Exploit

Fix

XSS

Weakness Enumeration

CWE-79

Related Identifiers

BDU:2026-03379

CVE-2025-66554

GHSA-9V78-CPFC-V6H2

Affected Products

Nextcloud Contacts

Red Os

References · 15

• 🔥 https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/66xxx/CVE-2025-66554.json · Exploit
• https://github.com/nextcloud/contacts/commit/d954d098978dde1f121600e8b994e02f293c68b1 · Patch
• https://github.com/nextcloud/contacts/pull/4619 · Patch
• https://github.com/nextcloud/security-advisories/security/advisories/GHSA-9v78-cpfc-v6h2 · Vendor Advisory
• http://repo.red-soft.ru/redos/8.0/x86_64/updates · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2025-66554 · Security Note
• https://hackerone.com/reports/3293290 · Vendor Advisory
• https://osv.dev/vulnerability/CVE-2025-66554 · Vendor Advisory
• https://bdu.fstec.ru/vul/2026-03379 · Security Note
• https://t.me/CVEtracker/38951 · Telegram Post
• https://twitter.com/CVEnew/status/1997009581965562136 · Twitter Post
• https://twitter.com/dailycve/status/1998491938111029374 · Twitter Post
• https://redos.red-soft.ru/support/secure/uyazvimosti/support/secure/uyazvimosti/uyazvimost-nextcloud-app-contacts-cve-2025-66554-7.3 · Note
• https://twitter.com/VulmonFeeds/status/1997130319061803314 · Twitter Post
• https://redos.red-soft.ru/support/secure/uyazvimosti/support/secure/uyazvimosti-red-os-8-0/uyazvimost-nextcloud-app-contacts-cve-2025-66554-8.0 · Note