EUVD-2026-20559
CVSS Vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:L/VI:N/VA:H/SC:L/SI:N/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Lifecycle Timeline
3Tags
Description
Zammad is a web based open source helpdesk/customer support system. Prior to 7.0.1 and 6.5.4, the webhook model was missing a proper validation for loop back addresses, or link-local addresses - only the URL scheme (HTTP/HTTPS) as well as the hostname was checked. This could end up in retrieving confidential metadata of cloud/hosting providers. The existing check is now extended and is applied when configuring webhooks as well as triggering webhook jobs. This vulnerability is fixed in 7.0.1 and 6.5.4.
Analysis
Server-side request forgery in Zammad webhook implementation allows authenticated administrators to retrieve confidential cloud provider metadata by exploiting insufficient validation of loopback and link-local addresses. Affects versions before 7.0.1 and 6.5.4. …
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Remediation
Within 24 hours: Identify all Zammad instances and document current versions (check Administration > System > About). Within 7 days: Upgrade to Zammad 7.0.1 or 6.5.4 or later; if upgrade is not immediately feasible, restrict webhook configuration access to a minimal set of trusted administrators and audit existing webhook URL configurations for suspicious internal/loopback IP targeting (169.254.x.x, 127.x.x.x, 10.x.x.x, 172.16-31.x.x, 192.168.x.x). …
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