Improper Validation of Specified Type of Input in Etherpad - CVE-2021-43802
Published: December 9, 2021 / Updated: April 17, 2026
Vulnerability identifier: #VU126467
CSH Severity: Medium
CVSSv4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2021-43802
CWE-ID: CWE-1287
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerable software:
Etherpad
Etherpad
Software vendor:
The Etherpad Foundation
The Etherpad Foundation
Description
The vulnerability allows a remote user to execute arbitrary code.
The vulnerability exists due to improper authorization in the *.etherpad import handling functionality when importing a crafted *.etherpad file. A remote user can import a specially crafted *.etherpad file to execute arbitrary code.
Exploitation to gain administrative privileges requires deleted or cleaned-up express-session state, such as via a plugin that deletes session state or a custom cleanup process. Even if access to /admin/* pages is blocked by a reverse proxy, the issue can still be used to crash Etherpad or bypass authorization checks to access restricted pads.
Remediation
Install security update from vendor's website.