Cisco IOS XE Software CLI Argument Injection Vulnerability

🚨SEVERITY: MEDIUM — CVSS 6.0Security Advisory

TL;DR 📌

  • A vulnerability in the CLI of Cisco IOS XE Software could allow an authenticated, local attacker with administrative privileges to execute arbitrary commands as root on the underlying operating system of an affected device. This vulnerability is due to insufficient validation of user arguments that are passed to specific CLI commands. An attacker could exploit…
  • Highest CVSS: 6.0 (Medium).
  • Check the advisory for fixed releases — remediation detail is in the vendor link below.
  • CVEs: CVE-2025-20338.

What it is

CVE-2025-20338 is a CLI argument injection flaw in Cisco IOS XE Software. It sits in the command-line interface itself, in how certain CLI commands validate the arguments passed to them.

To exploit it, an attacker needs to already be logged into the device CLI with valid administrative credentials (privilege level 15). From there, they can craft specific commands that pass unvalidated arguments through to the underlying operating system, resulting in arbitrary command execution as root.

This is a local, authenticated, privilege-escalation-style issue rather than a remote or unauthenticated one: the access path runs through the management plane, and it requires an attacker to already hold high-level administrative access before they can escalate to root on the underlying OS. Cisco states the vulnerability affects IOS XE Software regardless of device configuration, and has confirmed that IOS XR Software and NX-OS Software are not affected.

Cisco’s PSIRT says it is not aware of any public announcements or malicious use of this vulnerability.

What to do

  • Treat this as a privilege-escalation risk from admin to root, not a remote-access risk — prioritise it accordingly relative to other advisories in the same September 2025 IOS/IOS XE bundle.
  • Use the Cisco Software Checker to identify the fixed release for your specific train, and upgrade. Cisco has released software updates for this vulnerability, but the fixed version numbers aren’t listed for each release line in this advisory text — check the tool’s “First Fixed” and “Combined First Fixed” output for your running version.
  • No workarounds exist for this issue, so patching is the only remediation path.
  • Review who holds level-15 administrative access on IOS XE devices. Since exploitation requires those credentials, tightening administrative account issuance and use reduces exposure while you schedule the upgrade.
  • If you’re applying multiple advisories from the September 2025 bundled publication, use the Software Checker’s combined mode to find a single release that addresses all of them at once, rather than patching serially.

For leadership 🧭

Executive summary. This flaw lets someone who already holds top-level administrative CLI access on an IOS XE device escalate to root on the underlying operating system, turning a compromised or misused admin account into full device control. It requires no remote or unauthenticated access, so it should be scheduled alongside routine patching rather than treated as an emergency.

Why it matters:

  • Affects Cisco IOS XE Software regardless of device configuration, so exposure isn’t limited to specific features or setups.
  • Exploitation converts existing level-15 administrative CLI access into root-level control of the underlying OS, extending the damage any compromised or rogue admin account can do.
  • No workarounds exist, so devices remain exposed until the fixed software is installed.
  • IOS XR and NX-OS are confirmed unaffected, so remediation effort can be focused solely on IOS XE estate.

Now / Next / Later:

  • Now: Identify which IOS XE devices are running and review who currently holds level-15 administrative CLI access, tightening issuance where possible.
  • Next: Run affected IOS XE releases through the Cisco Software Checker to find the correct fixed version (or combined fix if applying other September 2025 bundle advisories) and schedule the upgrade.
  • Later: Establish a process for regularly auditing and minimising level-15 administrative accounts on network infrastructure, since this class of flaw depends entirely on that access level being available to an attacker.

Source