CVE-2020-26217

8.0 HIGH

Remote Code Execution Deserialization

📋 TL;DR

CVE-2020-26217 is a remote code execution vulnerability in XStream that allows attackers to execute arbitrary shell commands by manipulating processed input streams. Only users relying on blocklists are affected, while those using XStream's Security Framework allowlist are protected. The vulnerability exists in versions before 1.4.14.

💻 Affected Systems

Products:

XStream

Versions: All versions before 1.4.14

Operating Systems: All platforms running Java

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects users relying on blocklists; allowlist users are not vulnerable

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Full system compromise with attacker gaining shell access and executing arbitrary commands with application privileges

🟠

Likely Case

Remote code execution leading to data theft, system manipulation, or lateral movement within the network

🟢

If Mitigated

No impact if using XStream's Security Framework allowlist or properly configured blocklists

🌐 Internet-Facing: HIGH - Remote exploitation without authentication possible

🏢 Internal Only: MEDIUM - Requires attacker access to internal systems but can lead to lateral movement

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: LIKELY

Unauthenticated Exploit: ⚠️ Yes

Complexity: LOW

Exploit requires manipulating input streams; advisory includes proof-of-concept details

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 1.4.14

Vendor Advisory: https://github.com/x-stream/xstream/security/advisories/GHSA-mw36-7c6c-q4q2

Restart Required: Yes

Instructions:

1. Upgrade XStream to version 1.4.14 or later
2. Update dependencies in your project configuration
3. Restart affected applications
4. Verify the new version is being used

🔧 Temporary Workarounds

Implement Security Framework Allowlist

all

Configure XStream's Security Framework to use allowlists instead of blocklists

// Java code to set up allowlist
XStream xstream = new XStream();
xstream.allowTypes(new Class[]{MyType.class});

🧯 If You Can't Patch

Implement strict input validation and sanitization for all XStream input
Deploy network segmentation and restrict access to affected systems

🔍 How to Verify

Check if Vulnerable:

Check XStream version in project dependencies or classpath; versions <1.4.14 are vulnerable

Check Version:

Check Maven/Gradle dependencies or use: java -cp xstream.jar com.thoughtworks.xstream.XStream --version

Verify Fix Applied:

Verify XStream version is 1.4.14 or later and Security Framework allowlist is properly configured

📡 Detection & Monitoring

Log Indicators:

Unusual Java process spawning, unexpected shell commands in application logs, suspicious deserialization patterns

Network Indicators:

Unexpected outbound connections from Java applications, unusual network traffic patterns

SIEM Query:

source="application.logs" AND ("XStream" OR "deserialization") AND ("ProcessBuilder" OR "Runtime.exec" OR suspicious_command_patterns)

📊 Metadata

CVE ID: CVE-2020-26217

CVSS v3 Score: 8.0 (HIGH)

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

CWE: CWE-78

Published: November 16, 2020

Last Updated: May 23, 2025

🔗 References

https://github.com/x-stream/xstream/commit/0fec095d534126931c99fd38e9c6d41f5c685c1a Patch,Third Party Advisory
https://github.com/x-stream/xstream/security/advisories/GHSA-mw36-7c6c-q4q2 Mitigation,Third Party Advisory
https://lists.apache.org/thread.html/r2de526726e7f4db4a7cb91b7355070779f51a84fd985c6529c2f4e9e%40%3Cissues.activemq.apache.org%3E Issue Tracking,Mailing List
https://lists.apache.org/thread.html/r7c9fc255edc0b9cd9567093d131f6d33fde4c662aaf912460ef630e9%40%3Ccommits.camel.apache.org%3E Issue Tracking,Mailing List
https://lists.apache.org/thread.html/r826a006fda71cc96fc87b6eca4b5d195f19a292ad36cea501682c38c%40%3Cissues.activemq.apache.org%3E Issue Tracking,Mailing List
https://lists.apache.org/thread.html/redde3609b89b2a4ff18b536a06ef9a77deb93d47fda8ed28086fa8c3%40%3Cissues.activemq.apache.org%3E Issue Tracking,Mailing List
https://lists.debian.org/debian-lts-announce/2020/12/msg00001.html Mailing List,Third Party Advisory
https://security.netapp.com/advisory/ntap-20210409-0004/ Third Party Advisory
https://www.debian.org/security/2020/dsa-4811 Third Party Advisory
https://www.oracle.com//security-alerts/cpujul2021.html Patch,Third Party Advisory
https://www.oracle.com/security-alerts/cpuApr2021.html Patch,Third Party Advisory
https://www.oracle.com/security-alerts/cpuapr2022.html Not Applicable,Third Party Advisory
https://www.oracle.com/security-alerts/cpujan2022.html Not Applicable,Third Party Advisory
https://www.oracle.com/security-alerts/cpuoct2021.html Patch,Third Party Advisory
https://x-stream.github.io/CVE-2020-26217.html Exploit,Mitigation,Vendor Advisory
https://github.com/x-stream/xstream/commit/0fec095d534126931c99fd38e9c6d41f5c685c1a Patch,Third Party Advisory
https://github.com/x-stream/xstream/security/advisories/GHSA-mw36-7c6c-q4q2 Mitigation,Third Party Advisory
https://lists.apache.org/thread.html/r2de526726e7f4db4a7cb91b7355070779f51a84fd985c6529c2f4e9e%40%3Cissues.activemq.apache.org%3E Issue Tracking,Mailing List
https://lists.apache.org/thread.html/r7c9fc255edc0b9cd9567093d131f6d33fde4c662aaf912460ef630e9%40%3Ccommits.camel.apache.org%3E Issue Tracking,Mailing List
https://lists.apache.org/thread.html/r826a006fda71cc96fc87b6eca4b5d195f19a292ad36cea501682c38c%40%3Cissues.activemq.apache.org%3E Issue Tracking,Mailing List
https://lists.apache.org/thread.html/redde3609b89b2a4ff18b536a06ef9a77deb93d47fda8ed28086fa8c3%40%3Cissues.activemq.apache.org%3E Issue Tracking,Mailing List
https://lists.debian.org/debian-lts-announce/2020/12/msg00001.html Mailing List,Third Party Advisory
https://security.netapp.com/advisory/ntap-20210409-0004/ Third Party Advisory
https://www.debian.org/security/2020/dsa-4811 Third Party Advisory
https://www.oracle.com//security-alerts/cpujul2021.html Patch,Third Party Advisory
https://www.oracle.com/security-alerts/cpuApr2021.html Patch,Third Party Advisory
https://www.oracle.com/security-alerts/cpuapr2022.html Not Applicable,Third Party Advisory
https://www.oracle.com/security-alerts/cpujan2022.html Not Applicable,Third Party Advisory
https://www.oracle.com/security-alerts/cpuoct2021.html Patch,Third Party Advisory
https://x-stream.github.io/CVE-2020-26217.html Exploit,Mitigation,Vendor Advisory

📋 TL;DR

💻 Affected Systems

📦 What is this software?

Activemq by Apache

Activemq by Apache

Banking Cash Management by Oracle

Banking Cash Management by Oracle

Banking Cash Management by Oracle

Banking Corporate Lending Process Management by Oracle

Banking Corporate Lending Process Management by Oracle

Banking Corporate Lending Process Management by Oracle

Banking Credit Facilities Process Management by Oracle

Banking Credit Facilities Process Management by Oracle

Banking Credit Facilities Process Management by Oracle

Banking Platform by Oracle

Banking Platform by Oracle

Banking Platform by Oracle

Banking Supply Chain Finance by Oracle

Banking Supply Chain Finance by Oracle

Banking Supply Chain Finance by Oracle

Banking Trade Finance Process Management by Oracle

Banking Trade Finance Process Management by Oracle

Banking Trade Finance Process Management by Oracle

Banking Virtual Account Management by Oracle

Banking Virtual Account Management by Oracle

Banking Virtual Account Management by Oracle

Business Activity Monitoring by Oracle

Business Activity Monitoring by Oracle

Business Activity Monitoring by Oracle

Communications Policy Management by Oracle

Debian Linux by Debian

Debian Linux by Debian

Endeca Information Discovery Studio by Oracle

Retail Xstore Point Of Service by Oracle

Retail Xstore Point Of Service by Oracle

Retail Xstore Point Of Service by Oracle

Retail Xstore Point Of Service by Oracle

Snapmanager by Netapp

Snapmanager by Netapp

Xstream by Xstream

⚠️ Risk & Real-World Impact

Worst Case

Likely Case

If Mitigated

🎯 Exploit Status

🛠️ Fix & Mitigation

✅ Official Fix

Instructions:

🔧 Temporary Workarounds

Implement Security Framework Allowlist

🧯 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