CVE-2026-84458

What it is

Zammad is a web based open source helpdesk/customer support system. Prior to 7.1.2, when the "Automatic account link on initial logon" setting is enabled, Zammad binds an incoming third-party (SSO) identity to an existing local account by matching the email address the identity provider reports, without verifying that the provider actually confirmed ownership of that email. An attacker who controls any identity at a configured provider, including, by default, any Azure AD tenant via Zammad's multi-tenant Microsoft 365 /common app registration, can set that identity's email to a victim's address, authenticate, and be logged in as the victim. This bypasses the victim's local password entirely and affects any existing account, including agents and administrators. Zammad will honor the xms_edov ID token claim when email verification is required in the Microsoft 365 setting, treating a missing claim as unverified. This issue is fixed in version 7.1.2.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure, data tampering.

Exploit odds

0.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-09-25 19:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-09-28 14:45 UTC Last updatedMost recent change to the record

Details

Published

2026-09-25 19:17 UTC

Last modified

2026-09-28 14:45 UTC

Exploit probability

0.4% · EPSS, next 30 days

Weakness

CWE-287 · Improper authentication

Record status

Deferred

Attack profile CVSS 4.0 · 9.1

Attack vector

Network

Complexity

Low

Attack requirements

Present

Privileges needed

None

User interaction

None

Confidentiality

High

Integrity

High

Availability

None