CVE-2024-5171: Aomedia Libaom Buffer Overflow Flaw

CVE-2024-5171 Overview

An integer overflow vulnerability exists in the libaom library's internal function img_alloc_helper that can lead to a heap buffer overflow. This function is reachable via three callers: aom_img_alloc(), aom_img_wrap(), and aom_img_alloc_with_border(). When these functions are called with large values for parameters such as d_w, d_h, align, size_align, or border, integer overflows can occur in the calculations of buffer sizes and offsets, resulting in invalid fields in the returned aom_image_t struct and potential heap buffer overflow conditions.

Critical Impact

This critical vulnerability allows remote attackers to potentially achieve arbitrary code execution through crafted media files that trigger the integer overflow, leading to heap corruption in applications using the libaom AV1 codec library.

Affected Products

• aomedia libaom (all versions prior to patched releases)
• Applications and browsers utilizing libaom for AV1 video decoding
• Systems with Chromium-based browsers or other software depending on libaom

Discovery Timeline

• June 5, 2024 - CVE-2024-5171 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2024-5171

Vulnerability Analysis

The vulnerability stems from improper input validation (CWE-20) combined with integer overflow conditions (CWE-190) in the libaom codec library. The img_alloc_helper function performs arithmetic calculations on user-controlled parameters without adequate bounds checking. When large values are passed to the image allocation functions, the multiplication and addition operations used to calculate buffer sizes can wrap around due to integer overflow, resulting in allocation of insufficiently sized buffers.

This vulnerability is exploitable remotely through network-delivered media content. An attacker can craft malicious AV1 video files with specially constructed image dimension parameters that trigger the overflow condition. When a vulnerable application processes this content, the undersized buffer allocation followed by subsequent operations leads to heap buffer overflow, potentially enabling arbitrary code execution with the privileges of the affected application.

Root Cause

The root cause is insufficient validation of the d_w (display width), d_h (display height), align, size_align, and border parameters before they are used in arithmetic operations within img_alloc_helper. The function performs multiplications to calculate the required buffer size, but when these parameters are large enough, the result exceeds the maximum value that can be stored in the integer type, causing it to wrap around to a small positive value or even negative number when interpreted as signed.

Attack Vector

The attack vector is network-based, requiring no privileges or user interaction beyond the victim processing a malicious AV1 media file. An attacker could distribute malicious content through:

1. Compromised or malicious websites serving AV1 video content
2. Malicious media files shared via email, messaging, or file sharing platforms
3. Man-in-the-middle attacks on unencrypted media streams
4. Malicious advertisements containing embedded AV1 video

The vulnerability is triggered when the victim's application (browser, media player, video processing software) attempts to decode the malicious AV1 content using the vulnerable libaom library.

The exploitation mechanism involves passing carefully crafted large values to image allocation functions. When aom_img_alloc(), aom_img_wrap(), or aom_img_alloc_with_border() receive these values, the internal img_alloc_helper function calculates buffer sizes that overflow, leading to heap corruption. For detailed technical analysis, see the Chromium Issue Tracker Entry.

Detection Methods for CVE-2024-5171

Indicators of Compromise

• Abnormal crashes or unexpected termination of applications using libaom during AV1 media playback
• Memory corruption indicators in process memory dumps showing heap metadata corruption patterns
• Unusual network traffic retrieving AV1 video content from suspicious or newly registered domains
• Application error logs indicating allocation failures or heap corruption in media processing components

Detection Strategies

• Deploy endpoint detection and response (EDR) solutions to monitor for heap corruption exploitation patterns in media processing applications
• Implement network-based detection rules to identify AV1 video files with anomalous dimension parameters in headers
• Use SentinelOne's behavioral AI to detect post-exploitation activity following successful heap corruption
• Monitor for unusual process behavior including unexpected child process creation or memory injection following media playback

Monitoring Recommendations

• Enable crash dump collection and analysis for applications utilizing libaom to identify exploitation attempts
• Monitor system logs for segmentation faults or access violations in processes handling AV1 media
• Implement application-level monitoring to track memory allocation patterns in media processing workflows
• Utilize SentinelOne Singularity Platform for real-time detection of memory corruption exploitation techniques

How to Mitigate CVE-2024-5171

Immediate Actions Required

• Update libaom to the latest patched version on all affected systems
• Update Chromium-based browsers and other applications that bundle libaom
• Apply security updates from your Linux distribution (Fedora, Debian, etc.) that address this vulnerability
• Consider disabling AV1 codec support temporarily if immediate patching is not possible

Patch Information

Security patches are available through multiple distribution channels. Fedora has released package updates as announced in their security mailing list. Debian LTS users should refer to the Debian LTS Security Announcement for patching guidance. Organizations should prioritize updating all instances of libaom and dependent applications to remediate this critical vulnerability.

Workarounds

• Restrict AV1 video playback to trusted sources only while awaiting patch deployment
• Implement network-level filtering to block or quarantine AV1 content from untrusted sources
• Use sandboxing or containerization to isolate media processing applications
• Deploy SentinelOne agents with memory protection policies to detect and prevent heap exploitation attempts

# Check installed libaom version on Debian/Ubuntu systems
dpkg -l | grep libaom

# Update libaom on Debian/Ubuntu
sudo apt update && sudo apt upgrade libaom-dev libaom3

# Update libaom on Fedora
sudo dnf update libaom

# Verify the installed version after update
pkg-config --modversion aom