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Cisco Secure Client Multi-Version Analysis

Comprehensive reverse engineering and analysis of Cisco Secure Client (formerly AnyConnect) versions 4.9 through 5.1 for OpenConnect protocol interoperability.

Available Versions​

VersionNameAnalysis StatusDocumentation
5.1Cisco Secure Client 5.1✅ CompleteAnalysis
5.0Cisco Secure Client 5.0🔄 In ProgressAnalysis
4.10AnyConnect 4.10🔄 In ProgressAnalysis
4.9AnyConnect 4.9📋 PlannedAnalysis

Version Comparison​

See Version Comparison for detailed comparison across all versions (coming soon).

Purpose​

This analysis is conducted under DMCA §1201(f) for interoperability purposes, enabling the development of compatible open-source VPN server implementations.

Analysis Scope​

  • Protocol Specification: CSTP, DTLS, authentication methods
  • Cryptography: TLS/DTLS versions, cipher suites, certificate handling
  • Platform Coverage: Windows, Linux (x86_64, ARM64), macOS
  • Package Types: Predeploy (standalone), Webdeploy (server-side), Utilities

Latest Findings​

Version 5.1 (Latest)​

Release: 5.1.12.146 (September 2024) Analysis Date: October 30, 2025 Status: ✅ Complete

Key Findings:

  • ✅ TLS 1.3 support confirmed (preferred, with TLS 1.2 fallback)
  • ✅ 197 binaries analyzed (Linux x64, ARM64, Windows x64/ARM64, macOS)
  • ✅ Protocol 100% backward compatible with 4.x
  • ✅ New Linux ARM64 platform support
  • ✅ Modular architecture: DART, NVM (IPFIX), ISE Posture, ZTA
  • ✅ Boost C++ dependency introduced
  • ✅ OpenSSL 1.1.0+ required for TLS 1.3

See detailed 5.1 analysis →

Analysis Methodology​

All analyses are performed using professional reverse engineering tools:

Tools Used​

  • GNU Binutils: readelf, nm, objdump, strings
  • file: Binary identification
  • ldd: Dependency analysis
  • Python: Automated cataloging

Ethical Guidelines​

  • ✅ Analysis for interoperability purposes
  • ✅ Security research and protocol documentation
  • ✅ Server implementation compatibility testing
  • ❌ No malicious intent or exploitation
  • ❌ No proprietary code reproduction

Protocol Documentation​

See OpenConnect Protocol Reference for comprehensive protocol specifications.

For WolfGuard Developers​

Key insights from this analysis inform the WolfGuard server implementation:

  • Protocol compatibility matrices
  • Cipher suite selection
  • Authentication method support
  • Client feature expectations

Server Compatibility​

ocserv-modern​

Compatibility: ✅ Full support for Cisco Secure Client 5.1.12.146

Requirements:

  • WolfSSL 5.7.6 or later (TLS 1.3 support)
  • IPv6 dual-stack configuration
  • Optional: IPFIX collector for NVM telemetry
  • Optional: Cisco ISE integration for posture assessment

ocserv (vanilla)​

Compatibility: ⚠️ Partial support (TLS 1.2 only)

Limitations:

  • No TLS 1.3 support (GnuTLS limitation)
  • Client will fall back to TLS 1.2
  • No NVM/IPFIX support
  • No ISE Posture support
Legal Notice

All reverse engineering is performed for legitimate interoperability and security research purposes in compliance with applicable laws including DMCA §1201(f). No proprietary code is reproduced. Analysis is based on publicly available binaries. This documentation is not endorsed by Cisco Systems, Inc.

Contributing​

To contribute analysis or request specific version analysis:

  1. Open an issue at wolfguard-docs repository
  2. Provide version number and specific analysis requests
  3. Follow ethical guidelines for reverse engineering

Last Updated: October 30, 2025 Latest Version Analyzed: 5.1.12.146