CVE-2020-3327 – A heap buffer overflow vulnerability in ClamAV'... (How to Fix)

Q: What is the severity of CVE-2020-3327?

CVE-2020-3327 has a CVSS score of 7.5 (HIGH). A heap buffer overflow vulnerability in ClamAV's ARJ archive parsing module allows remote attackers to cause denial of service by crashing the scanning process. This affects ClamAV version 0.102.2 specifically. Any system using vulnerable ClamAV for scanning ARJ files is at risk.

📋 TL;DR

A heap buffer overflow vulnerability in ClamAV's ARJ archive parsing module allows remote attackers to cause denial of service by crashing the scanning process. This affects ClamAV version 0.102.2 specifically. Any system using vulnerable ClamAV for scanning ARJ files is at risk.

💻 Affected Systems

Products:

Clam AntiVirus (ClamAV)

Versions: Version 0.102.2 specifically

Operating Systems: All operating systems running ClamAV

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects systems where ClamAV is configured to scan ARJ archives. Many deployments have ARJ scanning enabled by default.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete denial of antivirus scanning service, potentially allowing malware to bypass detection while ClamAV is down.

🟠

Likely Case

ClamAV scanning process crashes when processing malicious ARJ files, requiring service restart and causing temporary scanning disruption.

🟢

If Mitigated

With proper network controls and updated software, impact is limited to isolated scanning failures with automatic service recovery.

🌐 Internet-Facing: MEDIUM - Exploitation requires sending crafted ARJ files to scanning services, which could be targeted via email gateways or web uploads.

🏢 Internal Only: LOW - Requires internal users to submit malicious ARJ files to scanning systems, which is less likely than external attacks.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: LIKELY

Unauthenticated Exploit: ⚠️ Yes

Complexity: LOW

Exploitation requires sending a specially crafted ARJ file to trigger the buffer overflow. No authentication needed if scanning service is accessible.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: ClamAV 0.102.3 and later

Vendor Advisory: https://blog.clamav.net/2020/05/clamav-01023-security-patch-released.html

Restart Required: Yes

Instructions:

1. Download ClamAV 0.102.3 or later from official sources. 2. Stop ClamAV services. 3. Install the updated version. 4. Update virus definitions. 5. Restart ClamAV services.

🔧 Temporary Workarounds

Disable ARJ scanning

all

Temporarily disable ARJ archive scanning in ClamAV configuration

Edit clamd.conf and add: ArchiveBlockEncrypted no
Or modify scanning rules to exclude .arj files

Network isolation

linux

Restrict network access to ClamAV scanning services

iptables -A INPUT -p tcp --dport 3310 -j DROP (for clamd)
Configure firewall to allow only trusted sources

🧯 If You Can't Patch

Implement network segmentation to limit access to ClamAV scanning services
Deploy intrusion detection systems to monitor for ARJ file submission attempts

🔍 How to Verify

Check if Vulnerable:

Run: clamscan --version | grep 'ClamAV 0.102.2'

Check Version:

clamscan --version

Verify Fix Applied:

Run: clamscan --version | grep -E 'ClamAV 0.102.[3-9]|ClamAV 0.10[3-9]|ClamAV [1-9]'

📡 Detection & Monitoring

Log Indicators:

ClamAV process crashes in system logs
Repeated ClamAV service restarts
ARJ file scanning failures

Network Indicators:

Unusual ARJ file submissions to scanning services
Multiple connection attempts to ClamAV ports

SIEM Query:

source="clamav.log" AND ("crash" OR "segmentation fault" OR "buffer overflow")

📊 Metadata

CVE ID: CVE-2020-3327

CVSS v3 Score: 7.5 (HIGH)

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

CWE: CWE-20

Published: May 13, 2020

Last Updated: November 21, 2024

🔗 References

https://blog.clamav.net/2020/05/clamav-01023-security-patch-released.html Vendor Advisory
https://lists.debian.org/debian-lts-announce/2020/05/msg00018.html Mailing List,Third Party Advisory
https://lists.debian.org/debian-lts-announce/2020/08/msg00010.html Mailing List,Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3BMTC7I5LGY4FCIZLHPNC4WWC6VNLFER/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/IJ67VH37NCG25PICGWFWZHSVG7PBT7MC/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L5YWYT27SBTV4RZSGFHIQUI4LQVFASWS/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QM7EXJHDEZJLWM2NKH6TCDXOBP5NNYIN/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ROBJOGJOT44MVDX7RQEACYHQN4LYW5RK/
https://security.gentoo.org/glsa/202007-23 Third Party Advisory
https://usn.ubuntu.com/4370-1/ Third Party Advisory
https://usn.ubuntu.com/4370-2/ Third Party Advisory
https://usn.ubuntu.com/4435-1/ Third Party Advisory
https://usn.ubuntu.com/4435-2/ Third Party Advisory
https://blog.clamav.net/2020/05/clamav-01023-security-patch-released.html Vendor Advisory
https://lists.debian.org/debian-lts-announce/2020/05/msg00018.html Mailing List,Third Party Advisory
https://lists.debian.org/debian-lts-announce/2020/08/msg00010.html Mailing List,Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3BMTC7I5LGY4FCIZLHPNC4WWC6VNLFER/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/IJ67VH37NCG25PICGWFWZHSVG7PBT7MC/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L5YWYT27SBTV4RZSGFHIQUI4LQVFASWS/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QM7EXJHDEZJLWM2NKH6TCDXOBP5NNYIN/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ROBJOGJOT44MVDX7RQEACYHQN4LYW5RK/
https://security.gentoo.org/glsa/202007-23 Third Party Advisory
https://usn.ubuntu.com/4370-1/ Third Party Advisory
https://usn.ubuntu.com/4370-2/ Third Party Advisory
https://usn.ubuntu.com/4435-1/ Third Party Advisory
https://usn.ubuntu.com/4435-2/ Third Party Advisory

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💻 Affected Systems

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⚠️ Risk & Real-World Impact

Worst Case

Likely Case

If Mitigated

🎯 Exploit Status

🛠️ Fix & Mitigation

✅ Official Fix

Instructions:

🔧 Temporary Workarounds

Disable ARJ scanning

Network isolation

🧯 If You Can't Patch

🔍 How to Verify

Check if Vulnerable:

Check Version:

Verify Fix Applied:

📡 Detection & Monitoring

Log Indicators:

Network Indicators:

SIEM Query:

📊 Metadata

🔗 References

📤 Share & Export

🔗 Related Vulnerabilities