Cisco Secure Firewall Management Center CommandSinkRmi Deserialization of Untrusted Data Remote Code Execution Vulnerability

September 16th, 2026
ZDI-26-709 ZDI-CAN-30946

CVE ID

CVE-2026-20242

CVSS Score

8.1 AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected Vendors

Cisco

Affected Products

Secure Firewall Management Center

Vulnerability Details

This vulnerability allows remote attackers to execute arbitrary code on affected installations of Cisco Secure Firewall Management Center. Authentication is not required to exploit this vulnerability.

The specific flaw exists within the CommandSinkRmi class. The issue results from the lack of proper validation of user-supplied data, which can result in deserialization of untrusted data. An attacker can leverage this vulnerability to execute code in the context of the www user.

Additional Details

Cisco has issued an update to correct this vulnerability. More details can be found at:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-fmc-javarce-y2NypXwk

Disclosure Timeline

  • 2026-05-20 - Vulnerability reported to vendor
  • 2026-09-16 - Coordinated public release of advisory
  • 2026-09-16 - Advisory Updated

Credit

Andy Niu of TrendAI Research

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