CVE-2021-1577
📋 TL;DR
This vulnerability allows unauthenticated remote attackers to read or write arbitrary files on Cisco APIC and Cloud APIC systems due to improper access control in a specific API endpoint. Attackers can exploit this by uploading files to affected devices, potentially compromising system integrity and confidentiality. Organizations using vulnerable Cisco APIC/Cloud APIC deployments are affected.
💻 Affected Systems
- Cisco Application Policy Infrastructure Controller (APIC)
- Cisco Cloud Application Policy Infrastructure Controller (Cloud APIC)
📦 What is this software?
Application Policy Infrastructure Controller by Cisco
View all CVEs affecting Application Policy Infrastructure Controller →
Application Policy Infrastructure Controller by Cisco
View all CVEs affecting Application Policy Infrastructure Controller →
Application Policy Infrastructure Controller by Cisco
View all CVEs affecting Application Policy Infrastructure Controller →
Cloud Application Policy Infrastructure Controller by Cisco
View all CVEs affecting Cloud Application Policy Infrastructure Controller →
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attackers to read sensitive configuration files, write malicious files, execute arbitrary code, and potentially gain full control of the APIC infrastructure.
Likely Case
Unauthorized file access leading to configuration theft, credential harvesting, or deployment of backdoors that could disrupt network operations.
If Mitigated
Limited impact with proper network segmentation and access controls preventing external exploitation, though internal threats may still exist.
🎯 Exploit Status
The vulnerability requires no authentication and involves simple API calls, making exploitation straightforward for attackers with network access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 5.2(1g) and later
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-capic-frw-Nt3RYxR2
Restart Required: Yes
Instructions:
1. Download the patched version from Cisco Software Center. 2. Backup current configuration. 3. Upgrade to version 5.2(1g) or later following Cisco's APIC upgrade procedures. 4. Verify the upgrade completed successfully.
🔧 Temporary Workarounds
Network Access Restriction
allRestrict network access to APIC management interfaces to trusted IP addresses only
Configure ACLs on network devices to limit access to APIC management IPs
🧯 If You Can't Patch
- Isolate APIC management interfaces from untrusted networks using firewall rules
- Implement strict network segmentation to limit which systems can communicate with APIC endpoints
🔍 How to Verify
Check if Vulnerable:
Check APIC version via GUI (System > Controller > Firmware) or CLI (show version) and compare to vulnerable versionsCheck Version:
show versionVerify Fix Applied:
Verify version is 5.2(1g) or later and test API endpoint access from unauthorized sources📡 Detection & Monitoring
Log Indicators:
- Unusual file upload activities via API
- Unauthenticated access attempts to vulnerable endpoint
- File system modifications from unexpected sources
Network Indicators:
- HTTP POST requests to vulnerable API endpoint from unauthorized sources
- Unusual file transfer patterns to/from APIC
SIEM Query:
source="apic" AND (http_method="POST" AND uri_contains="/api/" AND user="-")