CVE-2026-84465 — Zammad: S/MIME signature verification allows forged sender impersonation
Zammad is a web based open source helpdesk/customer support system. Prior to 7.1.2, when Zammad checks the digital signature on an incoming S/MIME-signed email, it does not veri…
Published: 2026-09-25 · CVSS: 7.1 · CVSS 4.0
Zammad is a web based open source helpdesk/customer support system. Prior to 7.1.2, when Zammad checks the digital signature on an incoming S/MIME-signed email, it does not verify that the signing certificate is genuinely trusted, it only checks whether a certificate with a matching name is already stored in the system. An attacker can create their own certificate using the name of a real, previously trusted sender and use it to send a forged email. Zammad will display that email with the same "validly signed" indicator as a genuine message from the real sender, even though the attacker never had access to that sender's actual certificate or private key. This issue is fixed in version 7.1.2.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7