CVE-2021-32707 Bypass of image blocking in Nextcloud Mail
Attackers can bypass image blocking in Nextcloud Mail via CSS background images, potentially revealing user read status.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2021-32707?
CVE-2021-32707 is a medium-severity vulnerability in nextcloud security-advisories, published on 12 Jul 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Nextcloud Mail is a mail app for Nextcloud. 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 a `background-image` CSS attribute. Note that the images were still passed through the Nextcloud image proxy, and thus there was no IP leakage. The issue was patched in version 1.9.6 and 1.10.0. No workarounds are known to exist.
Which versions are affected by CVE-2021-32707?
It affects 1 product.
Products include Nextcloud Mail.
How do I fix CVE-2021-32707?
No fix has been published for CVE-2021-32707 yet. Limit exposure of the affected software until one is available.
Is CVE-2021-32707 being exploited?
There is no known exploitation of CVE-2021-32707 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-xxp4-44xc-8crh.