CVE-2026-20316 — Cisco Secure Firewall Management Center (FMC): Cisco Secure Firewall Management Center Use of Hard-coded Password Vulnerability

1. Executive summary

CVE-2026-20316 is a use of hard-coded password vulnerability (CWE-259) in Cisco Secure Firewall Management Center (FMC) software. NVD assigns CVSS 5.3 (MEDIUM); however, Cisco rates the Security Impact Rating as High because the low-privileged static account can be combined with other FMC vulnerabilities for privilege escalation. CISA added the CVE to its Known Exploited Vulnerabilities (KEV) catalogue on 2026-07-29 and updated its coordinator record the same day to reflect active exploitation. EMEA financial services running affected FMC versions with internet-exposed management interfaces face unauthenticated remote access to sensitive firewall management data.

2. Regulatory framing

Article	Trigger (the fact in this item)	Practical impact
DORA Art. 19: reporting of major ICT-related incidents to competent authorities	CISA KEV record updated to active exploitation on 2026-07-29 for a security appliance that manages perimeter firewalls — potential compromise of a critical ICT function.	If an affected FMC instance is confirmed compromised or exploited, clients must assess whether the incident meets the major-incident classification criteria and report accordingly.
DORA Art. 24: digital operational resilience testing — general requirements	Active exploitation of a hard-coded credential flaw in a core network security management product within the known vulnerable version range.	Clients must verify FMC exposure and patch status as part of ongoing resilience testing; internet-exposed management interfaces require immediate validation.

3. Technical analysis & attack chain

Affected versions (from NVD CPE data)

FMC 7.0.0 through 7.0.9
FMC 7.2.0 through 7.2.11
FMC 7.3.0 through 7.3.1.2
FMC 7.4.0 through 7.4.7
FMC 10.0.0 through 10.0.1

Vulnerability mechanism

The FMC web interface contains static, hard-coded credentials for a low-privileged account. An unauthenticated, remote attacker can authenticate to the FMC management interface using these credentials. Successful exploitation grants the attacker logged-in access as the low-privileged user, enabling access to sensitive data within the impacted system. The attack requires no user interaction and is reachable over the network (CVSS vector implies AV:N/AC:L/PR:N/UI:N).

Attack chain (confirmed steps)

Reconnaissance: Attacker identifies an internet-exposed Cisco FMC management interface (typically HTTPS on port 443 or 8305).
Authentication: Attacker authenticates using the hard-coded static credentials for the low-privileged account — no brute-force or credential theft required.
Data access: Attacker accesses sensitive data within the FMC system as the low-privileged user.
Potential privilege escalation (per Cisco advisory): The low-privileged access can be combined with other Cisco Secure FMC vulnerabilities to elevate privileges, increasing the impact beyond read-only data access.

Severity discrepancy note: NVD assigns CVSS 5.3 MEDIUM. Cisco has assigned a Security Impact Rating of High, citing the chaining potential with other FMC vulnerabilities for privilege escalation. This advisory uses the NVD CVSS 5.3 MEDIUM as authoritative per verified reference data, but clients should weight the Cisco SIR of High in their risk decisions given the confirmed chaining path.

Exploitation status: CISA's KEV catalogue entry (added 2026-07-29) and CISA coordinator record (updated 2026-07-29, exploitation: "active") confirm active exploitation in the wild. BleepingComputer reports the vulnerability was exploited in zero-day attacks (single-sourced; verify before enforcement). No threat actor attribution is available in the provided source material; no MITRE ATT&CK actor profile is referenced. Attribution is unconfirmed.

Attack surface reduction: NVD notes that if the FMC management interface does not have public internet access, the attack surface associated with this vulnerability is reduced.

4. Mitigation & containment

P1 — Within 24 hours

Inventory and exposure assessment: Identify all Cisco FMC deployments in the estate. For each, determine whether the management interface is internet-exposed. Prioritise internet-facing instances immediately.
Restrict management interface access: Block all inbound access to FMC management interfaces from the internet. Limit access to specific management VLANs or jump hosts via firewall rules and ACLs. If the interface must be remotely accessible, require VPN or a bastion host.
Review authentication logs: Search FMC access logs for successful logins from unexpected source IPs or logins to low-privileged accounts that do not correspond to legitimate administrator activity. Look for authentication events in the period preceding 2026-07-29 (the KEV addition date) to detect pre-disclosure exploitation.

P2 — Within 72 hours

Apply vendor fix: Apply the Cisco-provided patch or fixed software version for CVE-2026-20316 on all affected FMC instances. Consult the Cisco security advisory for the specific fixed versions. Do not delay patching internet-facing instances beyond P1 containment.
Disable or rotate the static account: If a vendor patch is not yet available for a specific affected version, follow Cisco's interim mitigation guidance (if provided in their advisory) to disable or restrict the low-privileged static account.
Forensic triage: On any FMC instance with an internet-exposed management interface during the vulnerable window, conduct forensic triage per CISA's Forensics Triage Requirements referenced in the KEV entry. Look for evidence of post-authentication activity, data access, or privilege escalation attempts.

P3 — Within 7 days

Patch all remaining instances: Apply the vendor fix to all FMC deployments, including internal-only management interfaces, to eliminate the hard-coded credential risk entirely.
Validate hardening: Ensure FMC management interfaces are accessible only over dedicated management networks with restricted ACLs. Verify no FMC management interface is exposed to the internet unless explicitly justified and protected by additional controls.
Update asset and vulnerability management: Add CVE-2026-20316 to continuous vulnerability scanning rules for Cisco FMC. Ensure new FMC deployments are patched before commissioning.

5. Indicators of compromise

No atomic indicators of compromise (IPs, domains, hashes, file paths) are available in the source material.

Behavioural indicators

Behaviour	Where to observe	Confidence
Successful authentication to FMC web interface using the hard-coded low-privileged account	FMC web server access logs; authentication logs	High — consistent with vulnerability mechanism
Login events to low-privileged FMC accounts from previously unseen source IP addresses	FMC authentication logs; SIEM correlation	Medium — behavioural inference, not source-confirmed
Access to sensitive FMC data following authentication by a low-privileged account	FMC audit logs; data access logs	Medium — consistent with described impact

6. Detection

Insufficient indicators to author detection rules.

The source material does not contain specific artefacts (hard-coded username strings, file paths, registry keys, mutex names, or distinctive command-line content) that would enable a reliable YARA or Sigma rule. The hard-coded credentials themselves are not provided in the sources. Clients should monitor FMC authentication logs for logins to low-privileged accounts from untrusted or unexpected source IP addresses and alert on any successful authentication to accounts that should not have active sessions.

CVE assessment

1 referenced CVE — 1 actively exploited (CISA KEV)

CVE	CVSS	Exploited	EPSS	Summary
CVE-2026-20316	5.3 Medium	⚠ KEV 2026-07-29	—	A vulnerability in the web interface of Cisco Secure Firewall Management Center (FMC) Software could allow an unauthenticated,…

7. Sources

NVD — CVE-2026-20316 Detail — https://nvd.nist.gov/vuln/detail/CVE-2026-20316 — 2026-07-28
CISA Known Exploited Vulnerabilities Catalog — CVE-2026-20316 — https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-20316 — added 2026-07-29
BleepingComputer — "Cisco warns of FMC static credential flaw exploited in zero-day attacks" — https://www.bleepingcomputer.com/news/security/cisco-warns-of-fmc-static-credential-flaw-exploited-in-zero-day-attacks/ — 2026

8. Adverse Trace position

CVE-2026-20316 is a MEDIUM-severity vulnerability (CVSS 5.3, CWE-259) with confirmed active exploitation per CISA KEV. The CVSS score understates operational risk: Cisco's High SIR reflects a realistic chaining path to privilege escalation, and the product is a central management platform for perimeter firewalls — compromise of FMC has cascading impact on the security controls it manages. EMEA financial services with internet-exposed FMC management interfaces should treat this as an immediate containment priority. The attack requires no authentication and no user interaction; the only effective short-term control is interface restriction followed by vendor patch application. Attribution is unconfirmed — no actor or campaign details are available in the source material. Adverse Trace will monitor for emerging IOCs, actor attribution, and Cisco's fixed-version guidance, and will update this advisory if the threat picture evolves.

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Published via PulseTrace — Adverse Trace threat intelligence.