CVE-2026-102489: Zammad 6.3-6.5 session hijack leading to RCE as the zammad user

Exploited in the wild Critical 9.4 EPSS 22.5% Linux kernel

Zammad 6.3.0 to 6.5.4 has a session hijack (session fixation) flaw that leads to remote code execution as the zammad user; the code is also present in 7.0.0 to 7.1.x but not exploitable because of the newer runtime environment. DIVD found it after attackers used it, chained with the CVE-2026-102490 local root flaw, to breach DIVD in September 2026. Zammad hardened the code in 7.2.0 and shipped an emergency 6.5.5 release for the unsupported 6.5 series; CISA added it to the Known Exploited Vulnerabilities catalog on 2026-10-02.

What do these terms mean? CVE · CVSS score · exploited (KEV) · EPSS · backported fix · all terms

What to do now

  1. Check whether you run Linux kernel and which version (commands below).
  2. Install the fixed version for your system: see “Patch it” below.
  3. The package update restarts Zammad. Zammad 6.5.5 is only available from the new package repository: migrate the repository first (see Zammad host-upgrade/repository-migration docs).
  4. If you cannot patch today, apply the temporary mitigation below and patch as soon as possible.
  5. Because this flaw is being exploited, also check the server for signs of compromise.

Affected and fixed versions

Affected:

Fixed in:

Am I affected?

dpkg -l zammad | grep ^ii
rpm -q zammad

Patch it

Use the commands for your system. Distribution packages often keep an older version number with the fix backported, so compare with the fixed package versions in the table below, not only with the upstream version.

Debian
sudo systemctl stop zammad
# back up Zammad first
sudo apt update
sudo apt-mark hold zammad
sudo apt upgrade
sudo apt-mark unhold zammad
sudo apt upgrade
Ubuntu
sudo systemctl stop zammad
# back up Zammad first
sudo apt update
sudo apt-mark hold zammad
sudo apt upgrade
sudo apt-mark unhold zammad
sudo apt upgrade
RHEL, AlmaLinux, Rocky, Oracle
sudo systemctl stop zammad
# back up Zammad first
sudo dnf upgrade --exclude zammad
sudo dnf upgrade
Fedora
sudo dnf upgrade --refresh kernel
SUSE / openSUSE
sudo systemctl stop zammad
# back up Zammad first
sudo zypper refresh
sudo zypper addlock zammad
sudo zypper update
sudo zypper removelock zammad
sudo zypper update
Amazon Linux
sudo dnf upgrade --releasever=latest kernel kernel6.12
Arch Linux
sudo pacman -Syu
Alpine
apk update && apk upgrade linux-lts linux-virt
FreeBSD
not Linux

General update steps for every system are on the Linux and Unix & BSD pages; after updating, see which services to restart.

If you cannot patch yet

Look for signs of exploitation

CISA required action: 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.

https://zammad.com/en/product/releases/ ; https://community.zammad.org/t/take-care-local-privilege-escalation-cve-2026-102490-is-reported-as-being-actively-exploited/21297/2 ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2026-102489

Related vulnerabilities

Sources

Page generated automatically from official sources on 2026-11-03 18:05 UTC and reviewed by an editor. Always confirm with your vendor's advisory.