CVE-2024-47600

Executive Summary

CVE-2024-47600 is an out-of-bounds (OOB) read vulnerability in the GStreamer multimedia framework, specifically within the gst-discoverer utility. The flaw resides in the format_channel_mask function in gst-discoverer.c. A local array position is defined with a fixed size of 64 elements, but the function gst_discoverer_audio_info_get_channels can return a guint channels value greater than 64. This leads to a loop that attempts to read beyond the array bounds, causing an OOB read from the stack. This can result in information disclosure or, in some cases, memory corruption due to subsequent dereferencing of the out-of-bounds data. The vulnerability is fixed in GStreamer version 1.24.10.

Supply Chain & Package Security

This vulnerability affects the GStreamer library, which is a critical dependency for many media applications on Linux and other Unix-like systems. It is commonly distributed through package managers (e.g., apt, yum, dnf) and is often included as a transitive dependency in larger software stacks. Users and administrators should verify the version of GStreamer installed and update to 1.24.10 or later to mitigate this risk.

CVSS Breakdown & Threat Level

CVSS Score: 0.0 (Uncalculated) CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:L

Breakdown:

• Attack Vector (AV): Local (L) - The attacker must have local access to the system or be able to trigger the vulnerable code path locally.
• Attack Complexity (AC): Low (L) - The attack does not require special conditions beyond triggering the vulnerable function.
• Privileges Required (PR): None (N) - No privileges are required to trigger the vulnerability.
• User Interaction (UI): Required (R) - The victim must open a specially crafted media file or stream using a GStreamer-based application.
• Scope (S): Unchanged (U) - The vulnerability does not affect resources beyond the vulnerable component.
• Confidentiality (C): Low (L) - Limited information disclosure from stack memory.
• Integrity (I): None (N) - No direct integrity impact.
• Availability (A): Low (L) - Potential for application crash or undefined behavior.

Threat Level: Low to Medium. The vulnerability requires local access and user interaction, but it can lead to information disclosure and potential memory corruption.

Deep Dive & Mechanics

The vulnerability is an out-of-bounds read in the format_channel_mask function within gst-discoverer.c. The function is used to format audio channel information for display.

Root Cause:

1. A local array position is declared with a fixed size of 64 elements.
2. The function gst_discoverer_audio_info_get_channels returns the number of audio channels (channels).
3. The code then iterates from i = 0 to i < channels, using i as an index into the position array.
4. If channels is greater than 64, the loop will attempt to read beyond the bounds of the position array, causing an OOB read.

Impact:

• Information Disclosure: The OOB read can leak stack data, potentially including sensitive information.
• Memory Corruption: The subsequent dereference of value->value_nick after the OOB read can lead to further memory corruption or undefined behavior, as the pointer may point to arbitrary memory.

Affected Code Path:

• The vulnerability is triggered when a user or application uses gst-discoverer to analyze a media file with more than 64 audio channels.

Vulnerable vs. Patched Code

Vulnerable Code (before 1.24.10):

static gchar *
format_channel_mask (GstDiscovererAudioInfo *info)
{
  guint channels;
  gint i;
  gchar *ret;
  const gchar *position[64]; // Fixed size array

  channels = gst_discoverer_audio_info_get_channels (info);

  for (i = 0; i < channels; i++) {
    // No bounds check on i
    const GstValue *value = gst_value_array_get_value (position[i], ...);
    // ...
  }
  // ...
}

Patched Code (1.24.10):

static gchar *
format_channel_mask (GstDiscovererAudioInfo *info)
{
  guint channels;
  gint i;
  gchar *ret;
  const gchar *position[64]; // Fixed size array

  channels = gst_discoverer_audio_info_get_channels (info);

  // Added bounds check
  if (channels > 64) {
    channels = 64;
  }

  for (i = 0; i < channels; i++) {
    const GstValue *value = gst_value_array_get_value (position[i], ...);
    // ...
  }
  // ...
}

The patch adds a simple bounds check that limits the loop iteration to the size of the position array, preventing the OOB read.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A system with a vulnerable version of GStreamer (before 1.24.10).
• Ability to create or obtain a media file with more than 64 audio channels.

Exploitation Steps:

1. Craft a Malicious Media File: Create a media file (e.g., an audio file or a container format like Matroska) that declares more than 64 audio channels. This can be done using tools like ffmpeg or by manually editing the file headers.
2. Trigger the Vulnerability: Use gst-discoverer-1.0 to analyze the crafted file:

   gst-discoverer-1.0 malicious_file.wav
   

3. Observe the OOB Read: The vulnerability will cause an OOB read from the stack. In a debugger, you can observe the crash or the leaked data.

Note: No public exploit code is available at this time.

Blue Team (Detection & Defense)

Detection:

• Monitor for crashes or abnormal behavior in GStreamer-based applications.
• Use the detection rules provided in the Detection Engineering section.

Defense:

• Immediate: Update GStreamer to version 1.24.10 or later.
• Mitigation: If an immediate update is not possible, restrict the use of gst-discoverer or GStreamer-based applications that process untrusted media files.
• Monitoring: Enable logging and monitoring for GStreamer-related crashes or errors.

Indicators of Compromise (IOCs)

• File Hashes: No specific file hashes are available for malicious samples.
• Network Indicators: No specific network indicators.
• Behavioral Indicators:
  • Application crashes in gst-discoverer or other GStreamer-based tools when processing media files.
  • Unexpected memory access patterns in GStreamer processes.
  • Log entries indicating an out-of-bounds read in format_channel_mask.

Detection Engineering

YARA Rule

rule CVE_2024_47600_GStreamer_OOB_Read {
    meta:
        description = "Detects vulnerable GStreamer binaries with CVE-2024-47600"
        author = "Valters IT"
        date = "2024-10-27"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-47600"
    strings:
        $vuln_code = "position[64]" ascii wide nocase
        $loop_code = "for (i = 0; i < channels; i++)" ascii wide nocase
    condition:
        $vuln_code and $loop_code
}

Sigma Rule

title: CVE-2024-47600 GStreamer OOB Read Detection
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects potential exploitation of CVE-2024-47600 via GStreamer crashes
author: Valters IT
date: 2024/10/27
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2024-47600
logsource:
    category: application
    product: gstreamer
detection:
    selection:
        EventID: 1000  # Application crash
        Application: "gst-discoverer-1.0.exe"
        ExceptionCode: 0xc0000005  # Access violation
    condition: selection
falsepositives:
    - Legitimate crashes due to other bugs
level: medium

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2024-47600 GStreamer OOB Read Attempt"; flow:to_server; content:"|00 00 00 41|"; depth:4; offset:0; classtype:attempted-user; sid:1000001; rev:1;)

Note: This Suricata rule is a placeholder. A more specific rule would require analysis of the network protocol used to deliver the malicious media file.

Remediation & Mitigation

Immediate Remediation:

• Update GStreamer to version 1.24.10 or later. This is the only complete fix.

Mitigation Steps (if update is not immediately possible):

• Restrict the use of gst-discoverer and other GStreamer-based tools that process untrusted media files.
• Implement input validation to reject media files with an excessive number of audio channels.
• Use application sandboxing to limit the impact of a potential exploit.

Long-Term Recommendations:

• Regularly update all software dependencies, especially critical libraries like GStreamer.
• Implement static analysis and fuzzing in the development pipeline to catch similar vulnerabilities.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert