High

Privilege Escalation to Root in Cisco IOS XR CLI

IdentifiersCVE-2026-20040CWE-20

CVE-2026-20040 is a privilege-escalation vulnerability in the CLI of Cisco IOS XR Software. The flaw is caused by insufficient validation of user-supplied arguments passed to specific CLI commands. An authenticated local attacker with a low-privileged account can exploit the issue by entering crafted commands at the CLI prompt. Successful exploitation results in execution of arbitrary commands as root on the underlying operating system of the affected device.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation allows a low-privileged authenticated local user to elevate privileges to root on the underlying operating system and execute arbitrary commands. This can result in full compromise of the affected device, including unrestricted administrative control over the OS layer, potential modification of system configuration, installation of persistent tooling, disruption of routing functions, and access to sensitive device data.

Mitigation

If you can’t patch tonight, do this now.

Cisco stated there are no workarounds for CVE-2026-20040. The only effective mitigation identified in the provided content is to apply Cisco’s fixed software release or applicable SMU as soon as possible. In the interim, reducing access to local CLI accounts and limiting low-privileged shell/CLI access may reduce exposure, but no vendor-supported workaround is available.

Remediation

Patch, then assume compromise.

Cisco has released software updates to address this vulnerability. Administrators should upgrade affected Cisco IOS XR Software deployments to a fixed release as identified by Cisco in its advisory. Cisco indicated fixed releases include versions such as 25.2.21 or 25.4.2, and Software Maintenance Updates (SMUs) are available for some platforms. Upgrade to the vendor-provided fixed version is the recommended remediation.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType

Cisco SystemsIos Xr Softwareoperating_system

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

13 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

13 SOURCESView more in app

cyber security newsNews

Mar 12, 2026

Cisco IOS XR Software Vulnerability Allow Attacker to Execute Commands as Root

A high-severity local privilege-escalation vulnerability in Cisco IOS XR Software CLI argument validation that allows an authenticated low-privileged user to escalate to root and execute arbitrary commands on the underlying OS.

What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.

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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity11