CVE-2021-43802 Admin privilege escalation and arbitrary code execution via malicious *.etherpad imports
Attackers can escalate to admin and execute arbitrary code via malicious imports if session state is deleted, requiring specific cleanup configurations.
- 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-2021-43802?
CVE-2021-43802 is a critical vulnerability in etherpad-lite, published on 9 Dec 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Etherpad is a real-time collaborative editor. In versions prior to 1.8.16, an attacker can craft an `*.etherpad` file that, when imported, might allow the attacker to gain admin privileges for the Etherpad instance. This, in turn, can be used to install a malicious Etherpad plugin that can execute arbitrary code (including system commands). To gain privileges, the attacker must be able to trigger deletion of `express-session` state or wait for old `express-session` state to be cleaned up. Core Etherpad does not delete any `express-session` state, so the only known attacks require either a plugin that can delete session state or a custom cleanup process (such as a cron job that deletes old `sessionstorage:*` records). The problem has been fixed in version 1.8.16. If users cannot upgrade to 1.8.16 or install patches manually, several workarounds are available. Users may configure their reverse proxies to reject requests to `/p/*/import`, which will block all imports, not just `*.etherpad` imports; limit all users to read-only access; and/or prevent the reuse of `express_sid` cookie values that refer to deleted express-session state. More detailed information and general mitigation strategies may be found in the GitHub Security Advisory.
Which versions are affected by CVE-2021-43802?
It affects 1 product.
Products include Etherpad Etherpad.
How do I fix CVE-2021-43802?
No fix has been published for CVE-2021-43802 yet. Limit exposure of the affected software until one is available.
Is CVE-2021-43802 being exploited?
There is no known exploitation of CVE-2021-43802 in the wild and no public exploit code.
Other vulnerabilities in etherpad-lite
Sources
Also known as GHSA-w3g3-qf3g-2mqc.