SB2021030114 - Multiple vulnerabilities in Nextcloud Server

Description

This security bulletin contains information about 2 vulnerabilities.

1) Cross-site scripting (CVE-ID: CVE-2021-22878)

CWE-ID: CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:U/U:Clear

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 when renaming malicious file. 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 access control (CVE-ID: CVE-2021-22877)

CWE-ID: CWE-284 - Improper Access Control

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear

The vulnerability allows a remote user to gain unauthorized access to otherwise restricted functionality.

The vulnerability exists due to improper access restrictions. A remote administrator can populate own credentials for other users external storage configuration when they did not configure one yet.

Remediation

Install update from vendor's website.

References

• https://nextcloud.com/security/advisory/?id=NC-SA-2021-005
• https://nextcloud.com/security/advisory/?id=NC-SA-2021-004