CVE-2021-3246 – CVE-2021-3246 is a heap buffer overflow vulnera... (How to Fix)

Q: What is the severity of CVE-2021-3246?

CVE-2021-3246 has a CVSS score of 8.8 (HIGH). CVE-2021-3246 is a heap buffer overflow vulnerability in libsndfile's msadpcm_decode_block function that allows attackers to execute arbitrary code by providing a specially crafted WAV file. This affects any application or system that processes WAV files using vulnerable versions of libsndfile. The vulnerability is particularly dangerous because it can lead to remote code execution when processing untrusted audio files.

📋 TL;DR

CVE-2021-3246 is a heap buffer overflow vulnerability in libsndfile's msadpcm_decode_block function that allows attackers to execute arbitrary code by providing a specially crafted WAV file. This affects any application or system that processes WAV files using vulnerable versions of libsndfile. The vulnerability is particularly dangerous because it can lead to remote code execution when processing untrusted audio files.

💻 Affected Systems

Products:

libsndfile
Applications using libsndfile library

Versions: libsndfile 1.0.30 and earlier

Operating Systems: Linux, Unix-like systems, Windows, macOS

Default Config Vulnerable: ⚠️ Yes

Notes: Any application that uses libsndfile to process WAV files with MS ADPCM encoding is vulnerable. This includes media players, audio editors, and web applications that process uploaded audio files.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Remote code execution with full system compromise, allowing attackers to install malware, exfiltrate data, or pivot to other systems.

🟠

Likely Case

Application crash leading to denial of service, with potential for limited code execution depending on exploit sophistication.

🟢

If Mitigated

Application crash without code execution if exploit fails or mitigations like ASLR are effective.

🌐 Internet-Facing: MEDIUM

🏢 Internal Only: MEDIUM

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: LIKELY

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Exploitation requires crafting a malicious WAV file that triggers the buffer overflow. The vulnerability is in a widely used library, making it attractive for attackers.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: libsndfile 1.0.31 and later

Vendor Advisory: https://github.com/libsndfile/libsndfile/issues/687

Restart Required: Yes

Instructions:

1. Update libsndfile to version 1.0.31 or later using your system's package manager. 2. For Linux: Use apt-get upgrade libsndfile1 or yum update libsndfile. 3. Rebuild any applications that statically link libsndfile. 4. Restart affected services or applications.

🔧 Temporary Workarounds

Disable WAV file processing

all

Temporarily block or reject WAV files from being processed by vulnerable applications.

# Configure web application firewalls to block WAV uploads
# Modify application configuration to disable WAV support

Sandbox audio processing

linux

Run audio processing in isolated containers or sandboxes to limit potential damage.

# Use Docker containers with limited privileges for audio processing
# Implement seccomp or AppArmor profiles

🧯 If You Can't Patch

Implement strict input validation to reject malformed WAV files before processing.
Deploy runtime protection solutions like memory-safe execution environments or exploit mitigation tools.

🔍 How to Verify

Check if Vulnerable:

Check libsndfile version: dpkg -l libsndfile1 | grep Version or rpm -q libsndfile

Check Version:

dpkg -l libsndfile1 2>/dev/null || rpm -q libsndfile 2>/dev/null || libsndfile-config --version 2>/dev/null

Verify Fix Applied:

Verify version is 1.0.31 or later: libsndfile-config --version or sndfile-info --version

📡 Detection & Monitoring

Log Indicators:

Application crashes with segmentation faults when processing WAV files
Unexpected process termination in audio processing services

Network Indicators:

Unusual WAV file uploads to web applications
Suspicious audio file transfers to internal systems

SIEM Query:

source="application.log" AND ("segmentation fault" OR "SIGSEGV") AND "wav"

📊 Metadata

CVE ID: CVE-2021-3246

CVSS v3 Score: 8.8 (HIGH)

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

CWE: CWE-787

Published: July 20, 2021

Last Updated: November 21, 2024

🔗 References

https://github.com/libsndfile/libsndfile/issues/687 Exploit,Patch,Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/07/msg00024.html Mailing List,Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DLUDCEMMPRA3IYYYHVZUOUZXI65FU37V/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/T7LNW4AVDVL3BU3N3KGVFLTYFASBVCIF/
https://security.gentoo.org/glsa/202309-11
https://www.debian.org/security/2021/dsa-4947 Third Party Advisory
https://github.com/libsndfile/libsndfile/issues/687 Exploit,Patch,Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/07/msg00024.html Mailing List,Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DLUDCEMMPRA3IYYYHVZUOUZXI65FU37V/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/T7LNW4AVDVL3BU3N3KGVFLTYFASBVCIF/
https://security.gentoo.org/glsa/202309-11
https://www.debian.org/security/2021/dsa-4947 Third Party Advisory

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