Zammad GmbH · Zammad · Zammad GmbH Zammad Session Fixation Vulnerability
Verdict
Patch soon · actively exploited, reachable from the internet without credentials, and in the top half of CVEs by near-term exploitation probability
Added to CISA KEV 2026-10-02 · exploited in the wild for 6 days
CVSS 9.4 CRITICAL. The score is a summary; these three components are the part that decides whether something scanning the internet can use it.
| Attack vector | networkreachable over the network, with no local access needed |
|---|---|
| Privileges required | noneneeds no credentials at all |
| User interaction | passiveneeds a user to click, load or submit something first |
| Base vector | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:A/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:Y/R:X/V:C/RE:X/U:X |
| Weakness | CWE-384 |
This describes the vulnerability. It says nothing about whether your systems run it.
EPSS puts the probability of exploitation in the next 30 days at 0.0126, which places it in the top half of all tracked CVEs. The percentile is the more useful half: 0.18 in absolute terms sounds low until you know most of the internet-facing software in the world scores under that.
| EPSS probability | 0.0126 |
|---|---|
| Percentile | 0.686 — top half |
| Added to KEV | 2026-10-02 |
|---|---|
| Days exploited | 6 |
| Federal remediation due | not set |
| Ransomware use | no known ransomware campaign use |
Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
Zammad versions 6.3.0 to 6.5.4 are vulnerable a session hijack vulnerability that leads to remote code execution as the zammad user. The vulnerability is also present in version 7.0.0 to version 7.1.3, but not exploitable due to environment conditions.
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