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CVE-2026-20343

Cisco Secure Firewall Management Center Software Information Disclosure and Disk Denial of Service Vulnerability

Published: Sep 16, 2026Updated: Sep 18, 2026 Sources: CVE List NVDCWE-306
7.5HIGH
NVD MITRE
EPSS Score
0.4%
Top 61.5%
CISA KEV
Not in KEV
Exploits
0 Known
Remediation
No Fix Available
Self-Check
Not available

Description

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

AI Act now

Cisco 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.

Executive summary

Unauthenticated remote access to a critical FMC API allows sensitive-file disclosure and disk exhaustion through repeated requests, causing denial of service.

If affected, business impact
Restricted file exposureFirewall management outageNetwork administration disruptionRecovery and cleanup costs

What to do now

  1. Check whether your organization runs Cisco Secure Firewall Management Center (FMC), especially any internet-reachable management interface.
  2. 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.
  3. Restrict access to FMC management interfaces to trusted administrator networks and block public internet access.
  4. Watch FMC disk-space and availability alerts for unusual rapid storage consumption, then contact Cisco support if activity is found.
May need vendor / contractor work

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:NI:NA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:NIntegrity
None
A:HAvailability
High
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Weaknesses

CWE-306

Affected Products

Cisco
commercial·USaka cisco systems, cisco systems inc.
Cisco Secure Firewall Management Center (FMC)
Networking Infrastructure

Exploitability

0 exploit sources identified

Exploit details including PoC links, Metasploit modules, and scanner templates are available after registration.

View exploit details
Is your org exposed to CVE-2026-20343?Request an assessment to establish which checks are appropriate for your systems. Check my exposure

Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

2 techniques
Initial Access
View detailed technique mapping

References

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-fmc-mulivulns-4PsnFwvx
sec.cloudapps.cisco.com
News mentions
1

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