Cisco IOS Software Industrial Ethernet Switch Device Manager Denial of Service Vulnerability

🚨SEVERITY: HIGH — CVSS 7.7Security Advisory

TL;DR 📌

  • A vulnerability in the web UI of Cisco IOS Software could allow an authenticated, remote attacker with low privileges to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper input validation. An attacker could exploit this vulnerability by sending a crafted URL in an HTTP request. A…
  • Highest CVSS: 7.7 (High).
  • Check the advisory for fixed releases — remediation detail is in the vendor link below.
  • CVEs: CVE-2025-20327.

What it is

CVE-2025-20327 affects the web UI of Cisco IOS Software running on Industrial Ethernet switches: the IE 2000, IE 3010, IE 4000, IE 4010 and IE 5000 series. The flaw is due to improper input validation of URLs handled by the device’s HTTP server.

An authenticated, remote attacker with low privileges can send a crafted URL in an HTTP request to the device manager. This triggers a reload of the switch, producing a denial of service condition. The CVSS vector (AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H) confirms this is network-reachable, requires low privileges and no user interaction, and impacts availability only — there’s no data confidentiality or integrity impact, just the reload.

The vulnerability only applies where the HTTP Server feature is enabled — either ip http server or ip http secure-server in the running configuration. Cisco IOS XR, IOS XE and NX-OS are explicitly not affected; this is specific to classic Cisco IOS Software on these industrial switch platforms.

What to do

  • Check whether the HTTP Server feature is active: show running-config | include ip http server|secure|active. If either ip http server or ip http secure-server appears, the web UI is exposed.
  • If ip http server is present alongside ip http active-session-modules none, or ip http secure-server is present alongside ip http secure-active-session-modules none, the device is not exploitable over that respective protocol.
  • Where no such exclusion is configured, treat the switch as exposed on whichever of HTTP or HTTPS is enabled.
  • As an interim mitigation, disable the HTTP Server feature entirely with no ip http server and/or no ip http secure-server (both are needed if both services are running). Cisco states there is no other workaround.
  • Plan to move to a fixed software release. The advisory does not list specific fixed versions in this brief — use the Cisco Software Checker against your current release number to identify the “First Fixed” or “Combined First Fixed” release for your platform, and upgrade accordingly.
  • This advisory is part of Cisco’s September 2025 IOS/IOS XE bundled publication; if you’re patching Industrial Ethernet switches, check the bundle for other advisories that may apply to the same devices.

For leadership 🧭

Executive summary. Cisco Industrial Ethernet switches (IE 2000, 3010, 4000, 4010 and 5000 series) running IOS with the web UI enabled can be forced to reload by any authenticated user with low privileges, causing an outage on plant or industrial network segments. There is no workaround other than disabling the HTTP server, so switches should be checked and either mitigated or scheduled for upgrade promptly.

Why it matters:

  • Affects the device manager web UI on Industrial Ethernet switches (IE 2000/3010/4000/4010/5000), which often sit on operational technology or factory floor networks where downtime has physical consequences.
  • Exploitation only needs low-privilege, authenticated access and a single crafted HTTP request — no admin rights or user interaction required — making it easy to trigger by anyone with a valid but limited account.
  • The impact is a full device reload, not data theft, but a reload of a switch on an industrial segment can interrupt connected control or monitoring equipment.
  • No workaround exists beyond disabling the HTTP Server feature entirely, which removes the web management interface some teams rely on for day-to-day administration.

Now / Next / Later:

  • Now: Run ‘show running-config | include ip http server|secure|active’ on affected Industrial Ethernet switches to see if the HTTP Server feature is enabled and exposed.
  • Next: Where the web UI is exposed and not already excluded by the active-session-modules settings, disable it with ’no ip http server’ and/or ’no ip http secure-server’ as an interim mitigation, or restrict access to trusted management hosts if disabling isn’t feasible.
  • Later: Use the Cisco Software Checker to identify the fixed IOS release for each affected switch and schedule upgrades during a maintenance window, closing the exposure permanently rather than relying on the HTTP-disable mitigation.

Source