CVE-2026-20343
Cisco Secure Firewall Management Center Software Information Disclosure and Disk Denial of Service 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 your organization runs Cisco Secure Firewall Management Center (FMC), especially any internet-reachable management interface.
- Ask your Cisco support contact or IT provider whether your FMC version is affected by CVE-2026-20343; no fixed version has been published in the available information.
- Restrict access to FMC management interfaces to trusted administrator networks and block public internet access.
- Watch FMC disk-space and availability alerts for unusual rapid storage consumption, then contact Cisco support if activity is found.
What it is
From the CVE record
A vulnerability in a critical API for Cisco Secure FMC Software could allow an unauthenticated, remote attacker to download sensitive files and use unbounded disk space. This vulnerability exists because a critical API lacks authentication. An attacker could exploit this vulnerability by repeatedly invoking the API. A successful exploit could allow the attacker to download sensitive files that should be restricted and consume disk space so the device could become unresponsive, causing a DoS condition.
In plain language
Written by AI from the recordCisco Secure Firewall Management Center (FMC) has a serious flaw that can expose restricted files and make the system stop responding; businesses using it should act now.
Unauthenticated remote access to a critical FMC API allows sensitive-file disclosure and disk exhaustion through repeated requests, causing denial of service.
If you're affected
- Restricted file exposure
- Firewall management outage
- Network administration disruption
- Recovery and cleanup costs
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
0.4% chance of exploitation activity in the next 30 days, which ranks it in the 36th percentile of scored CVEs.
Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.
Lifecycle
5 events over 2 days, from the signal feeds we watch.
- 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:N/I:N/A:H
Scored 7.5 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 NoneNo confidentiality impact
- Integrity NoneNo integrity impact
- 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
Watch the software you run.
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