Cisco Secure Firewall Management Center Software Command Injection Vulnerability

🚨SEVERITY: MEDIUM — CVSS 4.9Security Advisory

TL;DR 📌

  • A vulnerability in the web-based management interface of Cisco Secure Firewall Management Center (FMC) Software could allow an authenticated, remote attacker with Administrator-level privileges to execute arbitrary commands on the underlying operating system. This vulnerability is due to insufficient input validation of certain HTTP request parameters that are sent to the web-based management interface. An…
  • Highest CVSS: 4.9 (Medium).
  • Check the advisory for fixed releases — remediation detail is in the vendor link below.
  • CVEs: CVE-2025-20306.

What it is

CVE-2025-20306 is a command injection vulnerability in the web-based management interface of Cisco Secure Firewall Management Center (FMC) Software. It stems from insufficient input validation of certain HTTP request parameters sent to that interface.

Exploitation requires an authenticated, remote attacker holding Administrator-level credentials. There is no unauthenticated path here — the attacker must already be logged in with admin rights before sending a crafted HTTP request to the management interface. Given that access, they can execute arbitrary commands on the underlying operating system as root.

Cisco notes that the vulnerability only affects FMC deployments where lockdown mode is enabled; lockdown mode is disabled by default. This is a notable inversion of the usual pattern: when lockdown mode is off, admin-level shell access is already available via the expert CLI command, so the bug matters specifically because lockdown mode is meant to restrict that shell access — and this flaw provides a way around that restriction via the web UI.

Cisco has confirmed that Secure Firewall ASA Software, Secure Firewall Threat Defense (FTD) Software, and Secure IPS/NGIPS are not affected. This is FMC-specific.

What to do

  • Check whether lockdown mode is enabled on your FMC deployments — if it is disabled, this specific issue does not apply, though lockdown mode’s usual root-shell protections still apply.
  • If lockdown mode is enabled, use the Cisco Software Checker against your running FMC release to identify the first fixed release for this advisory; no fixed version numbers are listed in the advisory text itself, so run the checker or consult the advisory’s Fixed Software section directly.
  • There are no workarounds — Cisco states this explicitly, so mitigation means patching, not configuration changes.
  • Tighten who holds Administrator-level credentials on FMC, since exploitation depends entirely on possessing that access level.
  • This advisory is bundled with the August 2025 Cisco Secure Firewall ASA, FMC, and FTD semiannual publication — worth checking the linked bundle for other advisories affecting the same management platform.

For leadership 🧭

Executive summary. An attacker who already holds Administrator credentials on Cisco Secure Firewall Management Center can use this flaw to gain root-level command execution, but only where lockdown mode is enabled. Since there is no workaround, affected deployments should schedule the fix in the next routine change window rather than treat it as an emergency.

Why it matters:

  • Only affects FMC deployments with lockdown mode enabled — the very setting meant to block root shell access via the expert CLI command is bypassed through this web UI flaw instead.
  • Successful exploitation grants arbitrary command execution as root on the FMC appliance’s underlying OS, not just the management application.
  • Requires Administrator-level credentials already in hand — this is a privilege-escalation-of-trust issue, not a route for unauthenticated attackers.
  • ASA, FTD, and Secure IPS/NGIPS are explicitly confirmed unaffected — exposure is limited to FMC software itself.

Now / Next / Later:

  • Now: Check whether lockdown mode is enabled on each FMC deployment; if disabled, this specific CVE does not apply to you.
  • Next: For FMC instances running with lockdown mode enabled, run the Cisco Software Checker against your current release to find the first fixed version and schedule the upgrade — there is no workaround to apply instead.
  • Later: Review and restrict who holds Administrator-level credentials on FMC, since exploitation depends entirely on that access level being available to an attacker.

Source