Zammad up to 7.1.1 Account Linking improper authentication

Summaryinfo

A vulnerability labeled as critical has been found in Zammad up to 7.1.1. The impacted element is an unknown function of the component Account Linking. The manipulation results in improper authentication. This vulnerability is identified as CVE-2026-84458. The attack can be executed remotely. There is not any exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in Zammad up to 7.1.1. It has been classified as critical. Affected is an unknown part of the component Account Linking. The manipulation with an unknown input leads to a improper authentication vulnerability. CWE is classifying the issue as CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-84458 since 09/01/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The technical details are unknown and an exploit is not available.

Upgrading to version 7.1.2 eliminates this vulnerability.

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Productinfo

Name

• Zammad

Version

• 7.1.0
• 7.1.1

License

• open-source

Website

• Product: https://github.com/zammad/zammad/

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