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CVE-2025-31478

Zulip Authentication Backend Configuration Bypass

No known exploitation. EPSS puts it in the 29th percentile. Fixed in 10.2.

CVSS 3.18.2HighEPSS percentile29th0.4% chance in 30 daysCISA KEVNot listedNo confirmed exploitation
No public exploit knownFix10.2Upgrade to this build

Published Updated Sources: CVE.org, NVD

NVD CVE.org

What to do

Find your product and version, then upgrade to the build on the right.

  • ZulipAffected: < 10.2Upgrade to: not statedStated by: CVE record
  • Zulip ServerAffected: < 10.2Upgrade to: 10.2Stated by: NVD

Versions as the sources state them. Full version matrix after sign-in

Is your organisation exposed?Request an assessment to establish which checks fit your systems.

What it is

From the CVE record

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.

In plain language

No plain-language summary for this CVE yet.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

EPSS29th
CISA KEV

Not in the catalog. CISA has not confirmed exploitation.

Public exploits

No public exploit or proof of concept found in the sources we track.

EPSS

0.4% chance of exploitation activity in the next 30 days, which ranks it in the 29th percentile of scored CVEs.

Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.

Lifecycle

4 events over 282 days, from the signal feeds we watch.

  1. Record updated
  2. Publishedweakness classified, att&ck mapped

Affected products

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

Scored 8.2 by NVD.

How it is reached

  • Attack Vector NetworkExploitable remotely over the network without any special conditions
  • Attack Complexity LowNo special conditions — the attack can be reliably reproduced
  • Privileges Required NoneNo authentication required — anyone can exploit this
  • User Interaction NoneNo user interaction needed — fully automated exploitation

Scope

  • Scope UnchangedImpact is limited to the vulnerable component itself

Impact if exploited

  • Confidentiality HighTotal information disclosure — all data in the component is compromised
  • Integrity LowData modification is possible but limited in scope or consequence
  • Availability NoneNo availability impact

Weaknesses

ATT&CK techniques

Mapped from the weaknesses above (CWE to ATT&CK), not observed in attacks.

Sources

References in the record

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We'll flag the next CVE, public exploit or patch for Zulip Server, not every advisory.