CVE-2021-39220 Bypass of image blocking in Nextcloud Mail
Attackers can bypass image blocking in Nextcloud Mail to leak user IP addresses and read state via relative protocol images.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2021-39220?
CVE-2021-39220 is a low-severity vulnerability in nextcloud security-advisories, published on 25 Oct 2021. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
Nextcloud is an open-source, self-hosted productivity platform The Nextcloud Mail application prior to versions 1.10.4 and 1.11.0 does by default not render images in emails to not leak the read state or user IP. The privacy filter failed to filter images with a relative protocol. It is recommended that the Nextcloud Mail application is upgraded to 1.10.4 or 1.11.0. There are no known workarounds aside from upgrading.
Which versions are affected by CVE-2021-39220?
It affects 1 product.
Products include Nextcloud Mail.
How do I fix CVE-2021-39220?
No fix has been published for CVE-2021-39220 yet. Limit exposure of the affected software until one is available.
Is CVE-2021-39220 being exploited?
There is no known exploitation of CVE-2021-39220 in the wild and no public exploit code.
Other vulnerabilities in nextcloud security-advisories
- CVE-2021-32652 Missing permission check on email metadata retrieval
- CVE-2022-31132 Unauthenticated SSRF in 3rd party module "cerdic/csstidy"
- CVE-2024-52508 Nextcloud Mail auto configurator can be tricked into sending account information to wrong servers
- CVE-2023-23943 Blind SSRF via server URL input in the Nextcloud Mail app
- CVE-2023-45660 Require strict cookies for image proxy requests in Nextcloud Mail
Sources
Also known as GHSA-6q9v-wm8r-rcv5.