SB2018082107 - Multiple vulnerabilities in Nextcloud Server

Description

This security bulletin contains information about 3 secuirty vulnerabilities.

1) Cross-site scripting (CVE-ID: CVE-2018-3780)

The disclosed vulnerability allows a remote attacker to perform cross-site scripting (XSS) attacks.

The vulnerability exists due to insufficient sanitization of user-supplied data. A remote attacker can trick the victim to follow a specially crafted link and execute arbitrary HTML and script code in user's browser in context of vulnerable website.

Successful exploitation of this vulnerability may allow a remote attacker to steal potentially sensitive information, change appearance of the web page, perform phishing and drive-by-download attacks.

2) Improper authentication (CVE-ID: CVE-2018-3775)

The disclosed vulnerability allows a remote attacker to bypass authentication on the target system.

The vulnerability exists due to improper authentication. A remote authenticated attacker that obtained user credentials can bypass the 2 Factor Authentication.

3) Improper input validation (CVE-ID: CVE-2018-3776)

The disclosed vulnerability allows a remote attacker to bypass security restrictions on the target system.

The vulnerability exists due to insufficient sanitization of user-supplied data passed to JSON encoder. A remote attacker can cause attacker's actions not being logged in the audit log.

Remediation

Install update from vendor's website.

References

• https://nextcloud.com/security/advisory/?id=NC-SA-2018-008
• https://nextcloud.com/security/advisory/?id=NC-SA-2018-007
• https://nextcloud.com/security/advisory/?id=NC-SA-2018-006