CVE-2026-20242
Cisco Secure Firewall Management Center Software Java Deserialization Remote Code Execution Vulnerability
Public exploit available. Not confirmed exploited in the wild yet. No fix published yet.
What to do
No fixed build or workaround is published yet. Limit exposure and watch for a patch.
Steps
Written by AI from the record- Check whether Cisco Secure Firewall Management Center (FMC) uses External Database Access and identify every host on its approved database access list.
- Confirm that only trusted, controlled hosts remain on that list; remove any unnecessary or untrusted entries.
- Restrict access to the FMC management interface and the affected service port so only required internal hosts can reach it.
- No fixed version is currently available; ask Cisco or your support provider for the vendor-approved remediation and apply it when released.
What it is
From the CVE record
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.
In plain language
Written by AI from the recordA critical flaw in Cisco Secure Firewall Management Center (FMC) can let a hostile approved database host take over the device, so businesses using that feature should act now.
Unauthenticated remote code execution as root is possible through insecure Java deserialization in FMC's External Database Access feature when an attacker controls a host on its external database access list.
If you're affected
- Full FMC takeover
- Firewall policy changes
- Network security disruption
- Sensitive configuration exposure
Exploitation
Where each signal puts this CVE on the scale from published to confirmed exploited.
- CISA KEV
Not in the catalog. CISA has not confirmed exploitation.
- Public exploits
0 sources with a proof of concept or module.
Exploit links, PoCs and Metasploit modules after sign-in- EPSS
0.6% chance of exploitation activity in the next 30 days, which ranks it in the 48th percentile of scored CVEs.
Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.
Lifecycle
6 events over 2 days, from the signal feeds we watch.
- Record updated
- Record updated
- Publishedweakness classified, att&ck mapped, record updated
Affected products
Technical detail
CVSS 3.1 vector
Open in the CVSS calculatorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Scored 9.8 by NVD.
How it is reached
- Attack Vector NetworkExploitable remotely over the network without any special conditions
- Attack Complexity LowNo special conditions — the attack can be reliably reproduced
- Privileges Required NoneNo authentication required — anyone can exploit this
- User Interaction NoneNo user interaction needed — fully automated exploitation
Scope
- Scope UnchangedImpact is limited to the vulnerable component itself
Impact if exploited
- Confidentiality HighTotal information disclosure — all data in the component is compromised
- Integrity HighTotal loss of integrity — attacker can modify any data in the component
- Availability HighTotal denial of service — the component is completely unavailable
Weaknesses
ATT&CK techniques
Mapped from the weaknesses above (CWE to ATT&CK), not observed in attacks.
Sources
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