Arch Linux Security Advisory ASA-202107-41
=========================================
Severity: Low
Date    : 2021-07-20
CVE-ID  : CVE-2021-32707
Package : nextcloud-app-mail
Type    : information disclosure
Remote  : Yes
Link    : https://security.archlinux.org/AVG-2145

Summary
======
The package nextcloud-app-mail before version 1.10.1-1 is vulnerable to
information disclosure.

Resolution
=========
Upgrade to 1.10.1-1.

# pacman -Syu "nextcloud-app-mail>=1.10.1-1"

The problem has been fixed upstream in version 1.10.1.

Workaround
=========
None.

Description
==========
In versions prior to 1.9.6, the Nextcloud Mail application does not, by
default, render images in emails to not leak the read state. The
privacy filter failed to filter images with `background-image` CSS
attribute. Note that the images were still passed through the Nextcloud
image proxy, and thus there was no IP leakage.

Impact
=====
A remote attacker could disclose whether an email message has been read
by embedding a remote CSS background image.

References
=========
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-xxp4-44xc-8crh
https://hackerone.com/reports/1215251
https://github.com/nextcloud/mail/pull/5189
https://github.com/nextcloud/mail/commit/e54c2331f4b98cc39a5b3899c8ed1468dfc5cc30
https://security.archlinux.org/CVE-2021-32707