zulip: Improper Authentication
CVE-2025-31478 is a high-severity improper authentication vulnerability in zulip, with a CVSS 3.1 base score of 8.2 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected zulip versions: < 10.2. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.37% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Zulip Server to 10.2 or a later version.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Zulip | zulip | < 10.2 | Not stated |
| Zulip | Zulip Server | before 10.2 | 10.2 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- LowLimited modification of data is possible.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N. Scored by CNA (github.com).
Official description
Zulip is an open-source team collaboration tool. Zulip supports a configuration where account creation is limited solely by being able to authenticate with a single-sign on authentication backend, meaning the organization places no restrictions on email address domains or invitations being required to join, but has disabled the EmailAuthBackend that is used for email/password authentication. A bug in the Zulip server means that it is possible to create an account in such organizations, without having an account with the configured SSO authentication backend. This issue is patched in version 10.2. A workaround includes requiring invitations to join the organization prevents the vulnerability from being accessed.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Authentication
When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.
How developers prevent this class of flaw
- Use an authentication framework or library such as the OWASP ESAPI Authentication feature.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
- github.com/zulip/zulip/security/advisories/GHSA-qxfv-j6vg-5rqcThird Party Advisory
Patches and release notes
Other vulnerabilities in zulip
- 9.1 Critical severity
- 7.1 High severity
- 8.8 High severity
- 7.4 High severity
- 9.8 Critical severity
Recent Improper Authentication vulnerabilities
- 9.6 Critical severity
- 9.3 Critical severity
- 8.2 High severity
- 9.1 Critical severity
- 9.8 Critical severity
- 9.8 Critical severity
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