CVE-2025-20131: Cisco ISE Authentication Bypass Vulnerability

CVE-2025-20131 Overview

Cisco disclosed CVE-2025-20131, an improper access control vulnerability in the web-based management interface of Cisco Identity Services Engine (ISE). The flaw stems from improper validation of the file copy function in the ISE graphical user interface (GUI). An authenticated remote attacker holding administrative privileges can upload arbitrary files to the affected device by sending a crafted file upload request. The weakness is tracked under [CWE-284: Improper Access Control].

Critical Impact
An authenticated administrator can place arbitrary files onto a Cisco ISE appliance, which can be used to tamper with configuration data or stage follow-on attacks against the network access control plane.

Affected Products

Cisco Identity Services Engine 3.1 (including patches 1 through 9)
Cisco Identity Services Engine 3.2 (including patches 1 through 6)
Cisco Identity Services Engine 3.3 (including patches 1 and 2)

Discovery Timeline

2025-08-20 - CVE-2025-20131 published to the National Vulnerability Database
2026-09-18 - Last updated in NVD database

Technical Details for CVE-2025-20131

Vulnerability Analysis

Cisco Identity Services Engine is a policy decision point that enforces network access control, authentication, authorization, and device posture for enterprise networks. The vulnerability resides in the GUI's file copy function, which fails to properly validate file upload requests submitted through the administrative interface.

An attacker authenticated with administrative credentials can craft a file upload request that bypasses the intended validation checks. On successful exploitation, arbitrary files can be written to the ISE appliance file system. Because ISE sits at the center of network access decisions, unauthorized file placement can be leveraged to influence policy, scripts, or configuration artifacts the appliance relies on.

Root Cause

The root cause is improper validation of input processed by the file copy function exposed in the ISE GUI. The function does not sufficiently restrict the type, destination, or contents of uploaded files, meeting the definition of [CWE-284: Improper Access Control]. Administrative authentication is required, but the control gap allows a legitimate admin session to perform file write operations outside the intended scope.

Attack Vector

Exploitation is performed over the network against the ISE administrative GUI. The attacker must first authenticate with administrative privileges, meaning the vulnerability chains most dangerously with credential compromise, insider misuse, or a prior privilege escalation. Once authenticated, the attacker issues a crafted HTTP request to the file upload functionality to deliver an arbitrary file to the appliance. No user interaction is required, and the integrity impact is high while confidentiality and availability are not directly affected per the published CVSS vector.

No public proof-of-concept exploit, CISA KEV listing, or Exploit-DB entry has been published for this CVE at the time of writing. See the Cisco Security Advisory: ISE File Upload Vulnerability for vendor-published technical details.

Detection Methods for CVE-2025-20131

Indicators of Compromise

Unexpected files appearing in ISE appliance directories, especially those written outside normal patch or backup workflows.
Administrative GUI sessions that issue file upload or file copy API calls from unusual source IP addresses or outside maintenance windows.
Audit log entries showing use of the file copy function immediately followed by configuration or service changes.

Detection Strategies

Correlate ISE administrative audit logs with network flow data to identify file upload requests from unexpected administrator accounts or hosts.
Baseline the normal frequency and source of file copy operations through the ISE GUI and alert on deviations.
Monitor for new or modified executable, script, or configuration files on ISE nodes using file integrity monitoring where supported.

Monitoring Recommendations

Forward ISE syslog and administrative audit logs to a centralized SIEM for retention and correlation.
Alert on administrative logins to ISE from geographies or networks that are not approved for management access.
Review privileged ISE account inventory regularly and remove accounts that are no longer required.

How to Mitigate CVE-2025-20131

Immediate Actions Required

Apply the fixed Cisco ISE software release identified in the Cisco Security Advisory: ISE File Upload Vulnerability.
Restrict access to the ISE administrative GUI to a dedicated management network and trusted jump hosts only.
Enforce multi-factor authentication for all ISE administrator accounts to limit the credential compromise paths that enable this attack.
Review ISE administrative accounts and revoke privileges that are not required for daily operations.

Patch Information

Cisco has released fixed software addressing CVE-2025-20131. Customers running ISE 3.1, 3.2, or 3.3 should upgrade to the patch level identified by Cisco in the vendor advisory. Refer to the Cisco Security Advisory: ISE File Upload Vulnerability for the specific fixed releases and upgrade guidance.

Workarounds

No vendor-supplied workaround is documented; Cisco recommends upgrading to a fixed release.
As a compensating control, limit who can authenticate to the ISE admin GUI and audit administrative actions involving file operations.
Segment ISE management interfaces from general user and server networks to reduce exposure if an administrator credential is compromised.

bash

# Configuration example
# Restrict ISE admin GUI access to a management subnet (illustrative ACL on an upstream device)
ip access-list extended ISE-ADMIN-ACCESS
 permit tcp 10.10.0.0 0.0.0.255 host <ISE-ADMIN-IP> eq 443
 deny   tcp any host <ISE-ADMIN-IP> eq 443 log
 permit ip any any