CVE-2026-76424: Cisco ISE REST API RCE Vulnerability

CVE-2026-76424 Overview

CVE-2026-76424 is a path traversal vulnerability in the REST API of Cisco Identity Services Engine (ISE). An authenticated remote attacker with valid administrative credentials can upload or copy arbitrary files to arbitrary locations on the affected device. Successful exploitation can lead to arbitrary command execution as the root user, resulting in full compromise of the ISE appliance. The flaw is tracked as [CWE-23: Relative Path Traversal] and stems from insufficient validation of file paths during API-driven file operations.

Critical Impact
An authenticated administrator can write files to arbitrary filesystem locations and execute commands as root, resulting in full device compromise.

Affected Products

Cisco Identity Services Engine (ISE) — REST API component
Refer to the Cisco Security Advisory for the definitive list of affected releases
Deployments exposing the ISE administrative REST API to internal management networks

Discovery Timeline

2026-09-16 - CVE-2026-76424 published to NVD
2026-09-17 - Last updated in NVD database

Technical Details for CVE-2026-76424

Vulnerability Analysis

The vulnerability resides in file-handling logic exposed through the Cisco ISE REST API. The API accepts a file upload or copy request that includes a destination path parameter. The application fails to sanitize traversal sequences within that parameter before performing the file operation. An attacker submits a crafted path containing directory traversal characters to escape the intended storage directory. The write operation runs with the privileges of the ISE service account, which maps to root on the underlying appliance. Overwriting scripts, configuration files, or scheduled task definitions in privileged locations converts the file write primitive into arbitrary command execution as root.

Root Cause

The root cause is improper input validation of user-supplied path components in REST API file operations, classified as [CWE-23]. The API does not canonicalize the destination path or restrict writes to an allowlisted directory before invoking filesystem calls.

Attack Vector

Exploitation requires network access to the ISE REST API and valid administrative credentials. The attacker authenticates to the API, then issues a file upload or copy request containing a crafted destination path. Because the attacker must already possess administrative credentials, exploitation scenarios typically involve compromised admin accounts, insider abuse, or chaining with a prior credential-exposure flaw. No user interaction is required. See the Cisco Security Advisory for protocol-level detail.

Detection Methods for CVE-2026-76424

Indicators of Compromise

REST API requests containing ../ sequences, encoded traversal patterns (%2e%2e%2f), or absolute paths in file-operation parameters
Unexpected files appearing outside standard ISE upload directories, particularly under /opt, /etc, or /root
New or modified cron entries, systemd unit files, or startup scripts on ISE nodes
Root-owned processes spawned from paths not associated with the standard ISE distribution

Detection Strategies

Enable REST API audit logging and alert on file-upload endpoints invoked with path parameters that include traversal metacharacters
Baseline the ISE appliance filesystem and alert on writes to directories outside the documented upload targets
Correlate administrative API authentication events with subsequent file-write API calls originating from unusual source IPs or off-hours sessions

Monitoring Recommendations

Forward ISE administrative and REST API logs to a centralized analytics platform for retention and correlation
Monitor administrative account usage for anomalous session locations, concurrent logins, or credential reuse across appliances
Alert on any process executing as root from non-standard directories on ISE nodes

How to Mitigate CVE-2026-76424

Immediate Actions Required

Apply the fixed Cisco ISE releases identified in the Cisco Security Advisory as the primary remediation
Restrict REST API access to a dedicated management network and trusted administrator jump hosts
Rotate all ISE administrative credentials and enforce multi-factor authentication for administrative logins
Audit existing administrator accounts and remove unused or excessive-privilege accounts

Patch Information

Cisco has published patched software versions in the Cisco Security Advisory cisco-sa-ise-multi-hrP9jQSQ. Administrators should consult the advisory for the fixed release train that matches their deployed version and follow Cisco's documented upgrade procedure. No official workaround is provided that fully addresses the vulnerability without upgrading.

Workarounds

Limit REST API exposure using access control lists so only designated management hosts can reach the API endpoints
Disable or tightly scope external API integrations that are not actively required
Review administrative session activity and investigate any file operations executed since the advisory publication date