Critical-Severity Improper Authentication Flaw in zulip Tracked as CVE-2026-102893
A newly published critical vulnerability in zulip carries a CVSS score of 9.1. Here is what is affected and how to respond.
Key points
- CVE-2026-102893 affects zulip.
- CVSS 9.1 (Critical).
- No exploitation confirmed yet.
A critical improper authentication tracked as CVE-2026-102893 has been published in the National Vulnerability Database for zulip, with a CVSS base score of 9.1.
At a glance
- CVE
- CVE-2026-102893
- Product
- zulip
- CVSS
- 9.1 Critical
- Weakness
- improper authentication
- Exploited
- No known exploitation
What is the vulnerability?
The NVD entry states: Zulip is an open-source team collaboration tool. In Zulip Server versions through 12.1, GenericOpenIdConnectBackend matches the identity provider email claim to an active account's delivery_email without rejecting an explicitly false email_verified claim. If a configured identity provider returns an email address that the authenticating user does not control together with email_verified=false, Zulip can log the user into the existing account for that address. Exploitation requires a misconfigured trusted identity provider, and deployments whose authoritative identity provider only emits email addresses controlled by the authenticating user are not affected. This issue is fixed in version 12.2.
Affected versions
| Vendor | Product | Versions |
|---|---|---|
| Zulip | zulip | < 12.2 |
Is it being exploited?
There is no public confirmation of exploitation at the time of publication. It does not appear in CISA's Known Exploited Vulnerabilities catalog. We will update this report if that changes.
What should you do?
- Identify whether the affected product and versions run in your environment.
- Apply the vendor update listed in the advisory as soon as it is available.
- Limit network exposure of the affected service until it is patched.
- Monitor the vendor advisory for updated guidance or exploitation reports.
What to do and how to stay safe: CVE-2026-102893
- Vulnerability severity scores ignore your specific architecture and context.
- Exploitability depends on network exposure and user behavior, not just code flaws.
- Prioritization requires continuous asset inventory and threat intelligence alignment.
Risk-based vulnerability management focuses your limited resources on the flaws that actually threaten your business. Start by mapping your critical assets and checking for active exploits to prioritize your backlog.
Step-by-step guide: Risk-Based Vulnerability Management: Prioritize Fixes by Actual Danger
General security guidance from the Threat Times newsroom. It is not confirmed advice from the organisations named in this story.
Frequently asked questions
What is CVE-2026-102893?
CVE-2026-102893 is a improper authentication vulnerability in zulip.
How severe is CVE-2026-102893?
It has a CVSS score of 9.1 Critical.
Is CVE-2026-102893 being exploited?
There is no public confirmation of exploitation at the time of publication.
