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Cisco Secure Firewall Management Center Software Java Deserialization Remote Code Execution Vulnerability

CVSS 3.1 9.8 CRITICALCheck source for fixed versionsKEV status unknown

cve-program · CVE-2026-20242

Published

A vulnerability in the External Database Access feature of Cisco Secure Firewall Management Center (FMC) Software could allow an unauthenticated, remote attacker to execute arbitrary commands as root on an affected device. This vulnerability is due to insecure deserialization of a user-supplied Java byte stream from a host that is configured in the external database access list. An attacker could exploit this vulnerability by sending a crafted, serialized Java byte stream to a specific TCP port of an affected device. A successful exploit could allow the attacker to execute arbitrary commands on the device and elevate privileges to root. Notes: This vulnerability can be exploited only by an attacker who has control of a host in the external database access list. If the FMC management interface does not have public internet access, the attack surface that is associated with this vulnerability is reduced.

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Affected versions, risk and source history

Exploitation and risk

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cve-program · CVE-2026-20242

Published

Cisco Secure Firewall Management Center Software Java Deserialization Remote Code Execution Vulnerability

A vulnerability in the External Database Access feature of Cisco Secure Firewall Management Center (FMC) Software could allow an unauthenticated, remote attacker to execute arbitrary commands as root on an affected device. This vulnerability is due to insecure deserialization of a user-supplied Java byte stream from a host that is configured in the external database access list. An attacker could exploit this vulnerability by sending a crafted, serialized Java byte stream to a specific TCP port of an affected device. A successful exploit could allow the attacker to execute arbitrary commands on the device and elevate privileges to root. Notes: This vulnerability can be exploited only by an attacker who has control of a host in the external database access list. If the FMC management interface does not have public internet access, the attack surface that is associated with this vulnerability is reduced.

Source published
16 Sep 2026 20:08:27 UTC
Source modified
18 Sep 2026 03:55:57 UTC
Saved here
23 Oct 2026 15:48:27 UTC
Source terms
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CVSS 3.1 · 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

ChangeIntel

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Sources read 13 Nov 05:08 UTC · 274 of 275 readable · 272 fully read · documentation 469/469 current