CVE-2019-20388
📋 TL;DR
This vulnerability in libxml2 2.9.10 causes a memory leak in the xmlSchemaValidateStream function when processing XML schemas. It affects any application using libxml2 for XML schema validation, potentially leading to denial of service through resource exhaustion. Systems running vulnerable versions of libxml2 are affected.
💻 Affected Systems
- libxml2
📦 What is this software?
Communications Cloud Native Core Network Function Cloud Native Environment by Oracle
View all CVEs affecting Communications Cloud Native Core Network Function Cloud Native Environment →
Enterprise Manager Base Platform by Oracle
Enterprise Manager Base Platform by Oracle
Fedora by Fedoraproject
Fedora by Fedoraproject
Fedora by Fedoraproject
Leap by Opensuse
Libxml2 by Xmlsoft
Ontap Select Deploy Administration Utility by Netapp
View all CVEs affecting Ontap Select Deploy Administration Utility →
Peoplesoft Enterprise Peopletools by Oracle
Snapdrive by Netapp
⚠️ Risk & Real-World Impact
Worst Case
Sustained exploitation could cause memory exhaustion leading to application crashes or system instability, resulting in denial of service.
Likely Case
Gradual memory consumption over time causing degraded performance or eventual application crashes in systems processing numerous XML schemas.
If Mitigated
Minimal impact with proper monitoring and resource limits in place; memory usage would be contained.
🎯 Exploit Status
Exploitation requires ability to trigger XML schema validation with malicious input; no authentication needed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: libxml2 2.9.10 with patch or later versions
Vendor Advisory: https://gitlab.gnome.org/GNOME/libxml2/merge_requests/68
Restart Required: Yes
Instructions:
1. Update libxml2 package using system package manager. 2. For Linux: 'sudo apt update && sudo apt upgrade libxml2' (Debian/Ubuntu) or 'sudo yum update libxml2' (RHEL/CentOS). 3. Restart affected applications/services using libxml2.
🔧 Temporary Workarounds
Limit XML schema processing
allRestrict or monitor XML schema validation operations to prevent excessive memory consumption
Implement application-level limits on XML schema processing frequency
Memory usage monitoring
linuxMonitor memory consumption of processes using libxml2 XML schema validation
Use monitoring tools like top, htop, or system monitoring solutions
🧯 If You Can't Patch
- Implement strict input validation and sanitization for XML schemas
- Deploy memory usage monitoring and alerting for processes using libxml2
🔍 How to Verify
Check if Vulnerable:
Check libxml2 version: 'xml2-config --version' or 'dpkg -l libxml2' or 'rpm -q libxml2'Check Version:
xml2-config --versionVerify Fix Applied:
Verify version is patched: version should not be exactly 2.9.10 without patch; check with package manager for applied updates📡 Detection & Monitoring
Log Indicators:
- Unusual memory consumption patterns in application logs
- Application crashes related to memory exhaustion
Network Indicators:
- Repeated XML schema validation requests to vulnerable endpoints
SIEM Query:
Process memory usage > threshold AND process name contains applications using libxml2🔗 References
- http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00047.html
- https://gitlab.gnome.org/GNOME/libxml2/merge_requests/68
- https://lists.debian.org/debian-lts-announce/2020/09/msg00009.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/545SPOI3ZPPNPX4TFRIVE4JVRTJRKULL/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/5R55ZR52RMBX24TQTWHCIWKJVRV6YAWI/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JDPF3AAVKUAKDYFMFKSIQSVVS3EEFPQH/
- https://security.gentoo.org/glsa/202010-04
- https://security.netapp.com/advisory/ntap-20200702-0005/
- https://www.oracle.com/security-alerts/cpuapr2022.html
- https://www.oracle.com/security-alerts/cpujul2020.html
- https://www.oracle.com/security-alerts/cpujul2022.html
- https://www.oracle.com/security-alerts/cpuoct2021.html
- http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00047.html
- https://gitlab.gnome.org/GNOME/libxml2/merge_requests/68
- https://lists.debian.org/debian-lts-announce/2020/09/msg00009.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/545SPOI3ZPPNPX4TFRIVE4JVRTJRKULL/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/5R55ZR52RMBX24TQTWHCIWKJVRV6YAWI/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JDPF3AAVKUAKDYFMFKSIQSVVS3EEFPQH/
- https://security.gentoo.org/glsa/202010-04
- https://security.netapp.com/advisory/ntap-20200702-0005/
- https://www.oracle.com/security-alerts/cpuapr2022.html
- https://www.oracle.com/security-alerts/cpujul2020.html
- https://www.oracle.com/security-alerts/cpujul2022.html
- https://www.oracle.com/security-alerts/cpuoct2021.html
