SB2021012518 - Multiple vulnerabilities in Nextcloud Server

Description

This security bulletin contains information about 2 secuirty vulnerabilities.

1) Resource management error (CVE-ID: CVE-2020-8293)

The vulnerability allows a remote user to perform a denial of service (DoS) attack.

The vulnerability exists due to improper management of internal resources within the application when storing data in workflow rules. A remote user can store a huge amount of data and perform a denial of service (DoS) attack.

2) Stored cross-site scripting (CVE-ID: CVE-2020-8294)

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

The vulnerability exists due to insufficient sanitization of user-supplied data in markdown file with Nextcloud Talk. A remote user can store 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.

Remediation

Install update from vendor's website.

References

• https://nextcloud.com/security/advisory/?id=NC-SA-2021-001
• https://hackerone.com/reports/1018146
• https://nextcloud.com/security/advisory/?id=NC-SA-2021-002
• https://hackerone.com/reports/1023787