SB2018080714 - Information disclosure vulnerabilities in Nextcloud Server

Description

This security bulletin contains information about 2 secuirty vulnerabilities.

1) Improper input validation (CVE-ID: CVE-2018-3761)

The vulnerability allows a remote attacker to obtain potentially sensitive information on the target system.

The vulnerability exists due to insufficient input validation. A remote attacker with access to the OAuth2 refresh token can trick the victim into opening a specially crafted data and obtain new tokens.

2) Information disclosure (CVE-ID: CVE-2018-3762)

The vulnerability allows a remote authenticated attacker to obtain potentially sensitive information on the target system.

The vulnerability exists due to a missing check for read permissions. A remote attacker who receive an incomming share containing files tagged can still request a preview for arbitrary files.

Remediation

Install update from vendor's website.

References

• https://nextcloud.com/security/advisory/?id=nc-sa-2018-003
• https://nextcloud.com/security/advisory/?id=nc-sa-2018-002