CVE-2026-20122 Overview
A vulnerability in the API of Cisco Catalyst SD-WAN Manager could allow an authenticated, remote attacker to overwrite arbitrary files on the local file system. This security flaw stems from improper file handling on the API interface of affected systems, enabling attackers with valid read-only credentials and API access to upload malicious files and potentially gain elevated privileges.
Critical Impact
Authenticated attackers can overwrite arbitrary files on affected Cisco Catalyst SD-WAN Manager systems and gain vmanage user privileges through improper file handling in the API interface.
Affected Products
- Cisco Catalyst SD-WAN Manager (vManage)
- Systems with API access enabled
- Deployments with read-only API credentials
Discovery Timeline
- 2026-02-25 - CVE-2026-20122 published to NVD
- 2026-02-25 - Last updated in NVD database
Technical Details for CVE-2026-20122
Vulnerability Analysis
This vulnerability is classified under CWE-648 (Incorrect Use of Privileged APIs), indicating a fundamental flaw in how the Cisco Catalyst SD-WAN Manager API handles file operations. The vulnerability exists because the API interface fails to properly validate and restrict file handling operations, allowing authenticated users with read-only credentials to perform write operations that should be outside their authorized scope.
The attack requires authentication with valid read-only API credentials, meaning the attacker must have some level of legitimate access to the system. However, the improper file handling allows these low-privileged users to bypass intended access controls and perform arbitrary file overwrites on the local file system.
Root Cause
The root cause of this vulnerability lies in the improper file handling mechanisms within the API interface of Cisco Catalyst SD-WAN Manager. The system fails to adequately validate file upload requests and does not properly enforce access controls based on user privilege levels. This allows users with read-only API access to upload files to locations they should not have write access to, ultimately enabling arbitrary file overwrite capabilities.
The vulnerability demonstrates a failure to implement proper authorization checks when processing file upload requests through the API, violating the principle of least privilege.
Attack Vector
The attack is network-based and requires the attacker to have authenticated access to the Cisco Catalyst SD-WAN Manager API with valid read-only credentials. The exploitation process involves:
- The attacker authenticates to the SD-WAN Manager API using valid read-only credentials
- The attacker crafts a malicious file upload request targeting the vulnerable API endpoint
- Due to improper file handling, the API accepts the upload and writes the file to an attacker-specified location
- By overwriting critical system files, the attacker can escalate privileges to vmanage user level
The vulnerability does not require user interaction and can be exploited remotely over the network. A successful exploit allows the attacker to overwrite arbitrary files on the affected system and gain vmanage user privileges, potentially leading to further compromise of the SD-WAN infrastructure.
Detection Methods for CVE-2026-20122
Indicators of Compromise
- Unexpected file modifications in system directories on Cisco Catalyst SD-WAN Manager systems
- Anomalous API requests from read-only user accounts attempting file upload operations
- Changes to system configuration files outside normal maintenance windows
- Authentication logs showing unusual patterns from accounts with read-only API access
Detection Strategies
- Monitor API access logs for file upload requests from accounts that should only have read-only permissions
- Implement file integrity monitoring on critical system directories to detect unauthorized modifications
- Review and audit API access patterns for anomalous behavior, particularly from service accounts
- Deploy network traffic analysis to identify unusual API call patterns to SD-WAN Manager endpoints
Monitoring Recommendations
- Enable detailed API logging on Cisco Catalyst SD-WAN Manager systems
- Configure alerting for file system changes in protected directories
- Implement user behavior analytics to detect privilege abuse from read-only accounts
- Regularly audit API credentials and access permissions to identify overly permissive configurations
How to Mitigate CVE-2026-20122
Immediate Actions Required
- Review and audit all API credentials with access to Cisco Catalyst SD-WAN Manager
- Restrict API access to only necessary users and services with appropriate privilege levels
- Implement network segmentation to limit API access to trusted management networks
- Apply the security patch from Cisco as soon as available
Patch Information
Cisco has released a security advisory addressing this vulnerability. Administrators should consult the Cisco Security Advisory for detailed patch information and affected version details. It is recommended to apply the latest software updates to remediate this vulnerability.
Workarounds
- Restrict API access to only trusted IP addresses using access control lists
- Disable API access for accounts that do not require it operationally
- Implement additional authentication controls such as multi-factor authentication for API access
- Monitor and alert on all API file operations until patches can be applied
# Example: Restrict API access to management network only
# Configure ACL on SD-WAN Manager to limit API access
# Consult Cisco documentation for specific configuration syntax
# Review API access logs for suspicious activity
show running-config | include api
show users
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
