CVE-2024-47606

Executive Summary

CVE-2024-47606 is a critical integer underflow vulnerability in GStreamer's qtdemux plugin, specifically within the qtdemux_parse_theora_extension function. The flaw allows an attacker to trigger a heap-based buffer overflow by crafting a malicious QuickTime (MOV/MP4) file containing a malformed Theora extension header. Successful exploitation can lead to arbitrary code execution in the context of the application using GStreamer (e.g., media players, browsers, or server-side processing pipelines). The vulnerability is fixed in GStreamer 1.24.10.

Supply Chain & Package Security

This vulnerability affects the GStreamer library, which is a core dependency for many Linux distributions, media frameworks (e.g., GNOME, KDE), and applications (e.g., Totem, Rhythmbox, Pitivi). It is also commonly used in embedded systems and IoT devices. The supply chain risk is high, as any application that links against a vulnerable version of GStreamer is exposed. Package maintainers should prioritize updating to 1.24.10 or applying the backported patch.

CVSS Breakdown & Threat Level

While no official CVSS vector is provided, based on the technical details, a reasonable assessment is:

• Attack Vector (AV): Network (AV:N) – the vulnerability can be triggered by opening a malicious file from a remote source.
• Attack Complexity (AC): Low (AC:L) – no special conditions required beyond file parsing.
• Privileges Required (PR): None (PR:N) – no authentication needed.
• User Interaction (UI): Required (UI:R) – the victim must open the malicious file.
• Scope (S): Unchanged (S:U) – the exploit affects the vulnerable component.
• Confidentiality (C): High (C:H) – arbitrary code execution can leak sensitive data.
• Integrity (I): High (I:H) – code execution allows data modification.
• Availability (A): High (A:H) – crash or denial of service possible.

Estimated CVSS Score: 7.8 (High)

Threat Level: Critical – due to the potential for remote code execution and the widespread use of GStreamer.

Deep Dive & Mechanics

The vulnerability resides in the qtdemux_parse_theora_extension function within gst-plugins-good/gst/isomp4/qtdemux.c. The function parses Theora video codec extension data from a QuickTime file.

Root Cause:

1. Integer Underflow: The function reads a 32-bit signed integer (gint size) from the file. If the value is manipulated to be negative (e.g., -6), an underflow occurs when it is used in a calculation.
2. Type Confusion: This negative size is then cast to a 64-bit unsigned integer (guint64) when passed to gst_buffer_new_and_alloc. The negative value becomes a very large unsigned number (e.g., 0xFFFFFFFFFFFFFFFA).
3. Heap Overflow: gst_buffer_new_and_alloc attempts to allocate a buffer of this huge size. However, due to internal alignment and header size additions, the actual allocation (slice_size) overflows and becomes a small value (e.g., 0x89 bytes). The subsequent memcpy operation then writes attacker-controlled data far beyond the allocated buffer, corrupting adjacent heap memory, including the GstMapInfo structure.
4. Function Pointer Hijack: When gst_memory_unmap is called, it dereferences a function pointer (mem->allocator->mem_unmap_full) from the corrupted GstMapInfo. By carefully crafting the heap layout, an attacker can overwrite this pointer to redirect execution to arbitrary code.

Attack Flow:

1. Attacker crafts a malicious MOV/MP4 file with a Theora extension header containing a negative size field.
2. Victim opens the file with a GStreamer-based application.
3. qtdemux parses the file, triggering the integer underflow.
4. A small heap buffer is allocated, but a large memcpy overwrites heap metadata and the GstMapInfo structure.
5. The overwritten function pointer is called, leading to arbitrary code execution.

Vulnerable vs. Patched Code

Vulnerable Code (before 1.24.10):

// In qtdemux_parse_theora_extension
gint size;
// ... read size from file as signed 32-bit integer
size = QT_UINT32 (data); // Can be negative
// ...
// size is used in a calculation that underflows
// ...
// Later, size is passed to gst_buffer_new_and_alloc
GstBuffer *buf = gst_buffer_new_and_alloc (size); // size is now a huge unsigned value

Patched Code (1.24.10):

// In qtdemux_parse_theora_extension
guint32 size;
// ... read size as unsigned 32-bit integer
size = QT_UINT32 (data); // Now properly unsigned
// ...
// Validation added to ensure size is within reasonable bounds
if (size > MAX_THEORA_EXTENSION_SIZE) {
    goto error;
}
// ...
GstBuffer *buf = gst_buffer_new_and_alloc (size); // Safe

The patch changes the size variable to guint32 (unsigned) and adds a bounds check to prevent the underflow and subsequent overflow.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• GStreamer version < 1.24.10 installed.
• A tool to craft malicious MOV/MP4 files (e.g., Python with struct module).

Exploit Concept:

1. Create a valid MP4 file with a Theora video track.
2. Modify the Theora extension header to set the size field to a negative value (e.g., -6).
3. Adjust the heap layout by adding padding data to ensure the GstMapInfo structure is placed at a predictable offset.
4. Embed shellcode or a ROP chain in the file data that will be copied during the overflow.
5. The overwritten function pointer will redirect execution to the attacker's payload.

Example Python Snippet (Conceptual):

import struct

def craft_malicious_file():
    # Build a minimal MP4 with a Theora track
    # ... (omitted for brevity)
    
    # Theora extension header with negative size
    theora_ext = struct.pack('>I', 0xFFFFFFFF)  # size = -1 (underflow)
    # ... rest of the header
    
    # Write to file
    with open('exploit.mov', 'wb') as f:
        f.write(mp4_data)

Note: A full working exploit is not provided due to ethical considerations. The above is for educational purposes only.

Blue Team (Detection & Defense)

Detection:

• Monitor for processes (e.g., totem, gst-launch-1.0) that crash with heap corruption errors.
• Use the YARA and Sigma rules provided in the Detection Engineering section.
• Enable GStreamer debug logging (GST_DEBUG=*qtdemux*:5) to capture suspicious parsing events.

Defense:

• Immediately update GStreamer to version 1.24.10 or later.
• If patching is not possible, consider disabling Theora support in qtdemux by removing or blacklisting the plugin.
• Use application sandboxing (e.g., Firejail, AppArmor) to limit the impact of code execution.
• Implement file scanning for known malicious patterns (e.g., negative size fields in Theora headers).

Indicators of Compromise (IOCs)

• File Hashes (SHA256): (Example – actual hashes will vary)
  • e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 (malicious.mov)
• Network: Outbound connections from media player processes to unexpected IPs (post-exploitation).
• Process: GStreamer processes (gst-launch-1.0, totem, etc.) crashing with SIGSEGV or SIGABRT.
• Memory: Heap corruption patterns in crash dumps, specifically in qtdemux allocations.
• Logs: GStreamer debug logs showing qtdemux_parse_theora_extension with unexpected size values.

Detection Engineering

YARA Rule

rule CVE_2024_47606_Theora_Underflow {
    meta:
        description = "Detects malicious MOV/MP4 files exploiting CVE-2024-47606"
        author = "Valters IT"
        date = "2024-10-27"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-47606"
    strings:
        $theora_magic = { 80 00 00 00 }  // Theora atom type (example)
        $negative_size = { FF FF FF FF } // Potential negative size field
    condition:
        $theora_magic and $negative_size
}

Sigma Rule

title: CVE-2024-47606 GStreamer Theora Extension Heap Overflow
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects potential exploitation of CVE-2024-47606 via process crash or abnormal memory allocation
author: Valters IT
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith:
            - '/gst-launch-1.0'
            - '/totem'
            - '/rhythmbox'
        CommandLine|contains: '*.mov'
    condition: selection
falsepositives:
    - Legitimate media file parsing
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-47606 GStreamer Theora Extension Heap Overflow Attempt"; flow:to_server; content:"|80 00 00 00|"; depth:4; content:"|FF FF FF FF|"; within:100; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Patch: Update GStreamer to version 1.24.10 or later. For distributions, apply the latest security updates.
   • Debian/Ubuntu: sudo apt update && sudo apt upgrade libgstreamer-plugins-good1.0-0
   • Red Hat/CentOS: sudo yum update gstreamer-plugins-good
   • Build from source: git clone https://gitlab.freedesktop.org/gstreamer/gstreamer.git && cd gstreamer && git checkout 1.24.10 && meson build && ninja -C build && sudo ninja -C build install
2. Workaround: If patching is delayed, disable the qtdemux plugin by renaming or removing the shared library file (e.g., /usr/lib/x86_64-linux-gnu/gstreamer-1.0/libgstisomp4.so). Note: This will break MP4/MOV playback.
3. Monitor: Review logs for any signs of exploitation attempts.

Long-Term Mitigations:

• Implement input validation for all file format parsers.
• Use memory-safe languages or add bounds checking in critical code paths.
• Regularly update all dependencies, especially media libraries.

Valters IT Signature

This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters-it.com.