CVE-2026-56727: Zammad: PGP signature spoofing via unvalidated verification return
Zammad is a web based open source helpdesk/customer support system. Prior to 7.0.2, summary In Zammad's inbound PGP email processing, the return value of the gpg verification call was silently discarded. Regardless of whether gpg reported a valid, invalid, or missing signature, the handler unconditionally wrote sign: { success: true, comment: "Good signature" } to the article's security preferences. Impact Any sender could tamper with the body of a multipart/signed PGP email, or craft a message with an entirely fabricated or mismatched signature, and Zammad would display it to the recipient as cryptographically verified with a "Good signature" label. Users and agents relying on Zammad's signature indicator to confirm message authenticity and integrity would be misled into trusting modified or forged content. The vulnerability affects all inbound PGP-signed emails processed while the PGP integration is enabled. This issue is fixed in version 7.0.2.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Zammadto a version that resolves this vulnerability.Fixed in 7.0.2
Event History
Frequently Asked Questions
Which deployments are affected?
All Zammad deployments processing inbound PGP-signed email while the PGP integration is enabled are affected prior to version 7.0.2. The issue concerns inbound email signature status shown in article security preferences.
What does an attacker need to do to exploit this?
An attacker only needs to send a multipart/signed PGP email with a tampered body, fabricated signature, or mismatched signature. Zammad could display the message as having a "Good signature" even when GPG reported the signature as invalid or missing.
What is the immediate mitigation if upgrading is not possible?
Disable the PGP integration or avoid relying on Zammad's signature indicator for inbound PGP-signed emails. Independently verify signatures before treating message content as authentic or intact.
How can we determine whether messages may have been misrepresented?
Review inbound PGP-signed emails processed before upgrading to 7.0.2, particularly any where agents relied on the displayed "Good signature" status. That status was not a reliable indication of GPG verification results in affected versions.