What’s Vulnerable › Vulnerabilities

CVE-2026-84465: Zammad: S/MIME signature verification allows forged sender impersonation

• Severity: high (CVSS 7.1 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-25 · updated 2026-09-29
• Weakness: CWE-290

Description

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.

Affected products

• zammad: before 7.1.2

References

• https://github.com/zammad/zammad/commit/9a07d0b8214ac4e8e10c23fce71d613bd0625524
• https://github.com/zammad/zammad/security/advisories/GHSA-m9ff-hjr3-93h4

Get alerted when CVE-2026-84465 or the next vulnerability affects your stack