Zammad Session Fixation and RCE Exposure (CVE-2026-102489)

Catalog analysis: CISA added this entry on October 02, 2026. The entry reflects catalog information retrieved on October 02, 2026, not a snapshot archived on the inclusion date. This site’s publication date is shown separately. Check current vendor guidance before acting.

What the vulnerability is

CVE-2026-102489 is a session fixation vulnerability (CWE-384) affecting Zammad. If exploited, this flaw can allow an attacker to achieve remote code execution (RCE) with the privileges of the zammad user. The risk profile is increased by the fact that this vulnerability can be chained with another flaw, CVE-2026-102490.

Exposure and applicability

This vulnerability applies to organizations deploying Zammad GmbH’s Zammad software. Because CISA has added this entry to the Known Exploited Vulnerabilities (KEV) catalog as of October 2, 2026, defenders should treat this as a high-priority exposure. The primary risk path involves session fixation leading to RCE; however, the potential for chaining with CVE-2026-102490 suggests that an attacker could potentially escalate their impact once initial access is achieved.

Remediation priorities

Our analysis indicates that remediation should be prioritized based on the asset’s internet exposure. The following actions are recommended to reduce risk:

1. Immediate Patching: Apply mitigations according to vendor instructions. This is the primary method for removing the underlying session fixation flaw.
2. Chain Analysis: Because CVE-2026-102489 can be chained with CVE-2026-102490, vulnerability management teams should verify the status of both vulnerabilities simultaneously. Addressing only one may leave a partial attack path open.
3. Forensic Triage: Given CISA’s requirement for forensic triage on this vulnerability, defenders should examine logs for indicators of session manipulation or unauthorized execution of commands by the zammad user before and after patching.

How to validate remediation

To assure that exposure has been reduced, defenders must move beyond simple version checks. We recommend the following validation approach:

• Configuration Audit: Verify that the specific mitigations outlined in the vendor’s release notes are active and correctly configured on all Zammad instances.
• Session Behavior Testing: In a staged environment, security teams should attempt to verify if session identifiers remain static or are properly regenerated upon authentication, as per the nature of session fixation flaws.
• Privilege Verification: Confirm that the zammad user account is restricted to the minimum necessary permissions to limit the potential impact of any residual RCE risk.

Limits and open questions

Applying a patch reduces the likelihood of exploitation but does not guarantee the total elimination of risk. Residual risk remains if the system was already compromised prior to patching, as session fixation may have allowed an attacker to establish persistence. It is currently unknown whether specific ransomware campaigns are actively leveraging this vulnerability. Furthermore, while CISA has set a remediation deadline of October 5, 2026, for federal agencies, non-federal organizations must determine their own urgency based on their specific threat model and exposure.

Source and editorial note

CVE-2026-102489: Zammad GmbH Zammad Session Fixation Vulnerability · Source date: October 02, 2026 · Retrieved October 02, 2026.

Material facts are tied to the cited primary source. Recommendations are independent defensive analysis unless attributed to the source. Confirm consequential decisions against current authoritative guidance.

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