CVE-2020-8450
📋 TL;DR
CVE-2020-8450 is a buffer overflow vulnerability in Squid proxy servers configured as reverse proxies. Remote attackers can exploit incorrect buffer management to crash Squid or potentially execute arbitrary code. This affects Squid instances acting as reverse proxies, which are commonly used for web acceleration and load balancing.
💻 Affected Systems
- Squid
📦 What is this software?
Fedora by Fedoraproject
Fedora by Fedoraproject
Leap by Opensuse
Squid by Squid Cache
Ubuntu Linux by Canonical
Ubuntu Linux by Canonical
Ubuntu Linux by Canonical
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, or deployment of persistent backdoors.
Likely Case
Denial of service through Squid crash, disrupting reverse proxy services and causing website/application downtime.
If Mitigated
Limited to service disruption if exploit attempts are blocked by network controls or if the system has memory protection mechanisms.
🎯 Exploit Status
The vulnerability is in buffer management code, making exploitation relatively straightforward for attackers with reverse proxy access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Squid 4.10 and later
Vendor Advisory: http://www.squid-cache.org/Advisories/SQUID-2020_1.txt
Restart Required: Yes
Instructions:
1. Backup current Squid configuration. 2. Upgrade to Squid 4.10 or later using your distribution's package manager. 3. Apply configuration patches if needed. 4. Restart Squid service. 5. Verify the service is running correctly.
🔧 Temporary Workarounds
Disable Reverse Proxy Functionality
linuxTemporarily disable Squid's reverse proxy configuration if not essential
# Edit squid.conf and comment out or remove http_port ... accel directives
# Then restart: systemctl restart squid
Network Access Restrictions
linuxLimit access to Squid reverse proxy ports to trusted sources only
# Example iptables rule: iptables -A INPUT -p tcp --dport 80 -s trusted_network -j ACCEPT
# Then: iptables -A INPUT -p tcp --dport 80 -j DROP
🧯 If You Can't Patch
- Implement strict network segmentation to limit access to Squid reverse proxy ports
- Deploy WAF or IPS solutions that can detect and block buffer overflow attempts
🔍 How to Verify
Check if Vulnerable:
Check Squid version: squid -v | grep Version. If version is earlier than 4.10 and configured as reverse proxy, the system is vulnerable.Check Version:
squid -v | grep VersionVerify Fix Applied:
After patching, verify version is 4.10 or later with: squid -v | grep Version. Also test reverse proxy functionality.📡 Detection & Monitoring
Log Indicators:
- Squid crash logs
- Unexpected termination messages in system logs
- Access logs showing malformed requests to reverse proxy ports
Network Indicators:
- Unusual traffic patterns to Squid reverse proxy ports
- Repeated connection attempts with malformed headers
SIEM Query:
source="squid" AND ("fatal" OR "crash" OR "segmentation fault")🔗 References
- http://lists.opensuse.org/opensuse-security-announce/2020-03/msg00012.html
- http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00010.html
- http://www.squid-cache.org/Advisories/SQUID-2020_1.txt
- http://www.squid-cache.org/Versions/v3/3.5/changesets/SQUID-2020_1.patch
- http://www.squid-cache.org/Versions/v3/3.5/changesets/squid-3.5-8e657e835965c3a011375feaa0359921c5b3e2dd.patch
- http://www.squid-cache.org/Versions/v4/changesets/SQUID-2020_1.patch
- http://www.squid-cache.org/Versions/v4/changesets/squid-4-b3a0719affab099c684f1cd62b79ab02816fa962.patch
- http://www.squid-cache.org/Versions/v4/changesets/squid-4-d8e4715992d0e530871519549add5519cbac0598.patch
- https://lists.debian.org/debian-lts-announce/2020/07/msg00009.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/G6W2IQ7QV2OGREFFUBNVZIDD3RJBDE4R/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TSU6SPANL27AGK5PCGBJOKG4LUWA555J/
- https://security.gentoo.org/glsa/202003-34
- https://security.netapp.com/advisory/ntap-20210304-0002/
- https://usn.ubuntu.com/4289-1/
- https://www.debian.org/security/2020/dsa-4682
- http://lists.opensuse.org/opensuse-security-announce/2020-03/msg00012.html
- http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00010.html
- http://www.squid-cache.org/Advisories/SQUID-2020_1.txt
- http://www.squid-cache.org/Versions/v3/3.5/changesets/SQUID-2020_1.patch
- http://www.squid-cache.org/Versions/v3/3.5/changesets/squid-3.5-8e657e835965c3a011375feaa0359921c5b3e2dd.patch
- http://www.squid-cache.org/Versions/v4/changesets/SQUID-2020_1.patch
- http://www.squid-cache.org/Versions/v4/changesets/squid-4-b3a0719affab099c684f1cd62b79ab02816fa962.patch
- http://www.squid-cache.org/Versions/v4/changesets/squid-4-d8e4715992d0e530871519549add5519cbac0598.patch
- https://lists.debian.org/debian-lts-announce/2020/07/msg00009.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/G6W2IQ7QV2OGREFFUBNVZIDD3RJBDE4R/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TSU6SPANL27AGK5PCGBJOKG4LUWA555J/
- https://security.gentoo.org/glsa/202003-34
- https://security.netapp.com/advisory/ntap-20210304-0002/
- https://usn.ubuntu.com/4289-1/
- https://www.debian.org/security/2020/dsa-4682
