CVE-2021-43791
Published: 02 December 2021
Summary
CVE-2021-43791 is a medium-severity Insufficient Session Expiration (CWE-613) vulnerability in Zulip Zulip. Its CVSS base score is 6.5 (Medium).
Operationally, ranked at the 40.6th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2021-30687
Vulnerability details
Zulip is an open source group chat application that combines real-time chat with threaded conversations. In affected versions expiration dates on the confirmation objects associated with email invitations were not enforced properly in the new account registration flow. A confirmation…
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link takes a user to the check_prereg_key_and_redirect endpoint, before getting redirected to POST to /accounts/register/. The problem was that validation was happening in the check_prereg_key_and_redirect part and not in /accounts/register/ - meaning that one could submit an expired confirmation key and be able to register. The issue is fixed in Zulip 4.8. There are no known workarounds and users are advised to upgrade as soon as possible.
- CWE(s)
Related Threats
No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Locks the device (typically after inactivity) until re-authentication, addressing insufficient session expiration by preventing indefinite access.
Automatically terminating sessions after a defined period directly enforces session expiration, preventing indefinite session lifetimes that attackers can exploit.
Re-authentication after inactivity or time-based triggers prevents indefinite use of potentially hijacked or stale sessions.
Terminating sessions and network connections upon completion prevents insufficient session expiration.
Directly enforces termination of network sessions after inactivity or end-of-session, preventing indefinite session lifetime.
Consistent clocks across systems allow session expiration and timeout enforcement to function as intended in distributed environments.
When the non-persistent artifact is a session or connection, mandatory termination implements the missing expiration that CWE-613 describes.
Timed refresh of session-related information or on-demand generation plus deletion implements proper session expiration.