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Xstream CVE-2020-26259

MEDIUM
OS Command Injection (CWE-78)
2020-12-16 security-advisories@github.com
6.8
CVSS 3.1 · NVD
View

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V1 - Encoding and Sanitization OS command sanitization, avoid shell exec
MITRE ATT&CK

2 techniques across 1 tactic: Execution

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Impact

CVSS score of 6.8 (MEDIUM). Attack characteristics: network attack vector, high complexity, no privileges required, no user interaction not required. Public proof-of-concept exploit code is available.

Exploit ScenarioDerived

A remote attacker could execute arbitrary operating system commands on the host by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 82.4% exploitation probability (EPSS)

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AnalysisAI

XStream is a Java library to serialize objects to XML and back again. Rated medium severity (CVSS 6.8), this vulnerability is remotely exploitable, no authentication required. Public exploit code available and no vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Avoid passing user input to shell commands. Use language-specific APIs instead of shell execution. Apply strict input validation with allowlists.

Affected Packages

maven com.thoughtworks.xstream:xstream fix: 1.4.15

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in maven

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified as OS Command Injection (CWE-78), which allows attackers to execute arbitrary operating system commands on the host. XStream is a Java library to serialize objects to XML and back again. In XStream before version 1.4.15, is vulnerable to an Arbitrary File Deletion on the local host when unmarshalling. The vulnerability may allow a remote attacker to delete arbitrary know files on the host as log as the executing process has sufficient rights only by manipulating the processed input stream. If you rely on XStream's default blacklist of the Security Framework, you will have to use at least version 1.4.15. The reported vulnerability does not exist running Java 15 or higher. No user is affected, who followed the recommendation to setup XStream's Security Framework with a whitelist! Anyone relying on XStream's default blacklist can immediately switch to a whilelist for the allowed types to avoid the vulnerability. Users of XStream 1.4.14 or below who still want to use XStream default blacklist can use a workaround described in more detailed in the referenced advisories. Affected products include: Apache Struts, Xstream, Debian Debian Linux, Fedoraproject Fedora. Version information: version 1.4.15.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 6.8 MEDIUM
AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
None
Integrity
High
Availability
None

DescriptionNVD

XStream is a Java library to serialize objects to XML and back again. In XStream before version 1.4.15, is vulnerable to an Arbitrary File Deletion on the local host when unmarshalling. The vulnerability may allow a remote attacker to delete arbitrary know files on the host as log as the executing process has sufficient rights only by manipulating the processed input stream. If you rely on XStream's default blacklist of the Security Framework, you will have to use at least version 1.4.15. The reported vulnerability does not exist running Java 15 or higher. No user is affected, who followed the recommendation to setup XStream's Security Framework with a whitelist! Anyone relying on XStream's default blacklist can immediately switch to a whilelist for the allowed types to avoid the vulnerability. Users of XStream 1.4.14 or below who still want to use XStream default blacklist can use a workaround described in more detailed in the referenced advisories.

Threat Intelligence Overview

Threat Score
5.3/10
Composite threat intelligence
EPSS Score
82.4%
Top 0% exploitable
Exploit
POC
Public exploit code exists
Data Quality
4 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC Yes
EPSS 82.4%
Patch available Yes
Active threat Yes
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
Poc
System Exposure· derived
Open
Automatable· derived
No
Human Impact· derived
Medium

Priority Score

136
Low Medium High Critical
KEV: 0
EPSS: +82
CVSS: +34
PoC: +20
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

OS command injection occurs when an application passes unsanitized user input directly into system shell commands.

Affected Products (CPE)NVD

cpe:2.3:a:apache:struts:*:*:*:*:*:*:*:*
cpe:2.3:a:xstream:xstream:*:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*
CVE-2020-26217 HIGH POC
8.8 Nov 16

XStream before version 1.4.14 is vulnerable to Remote Code Execution.The vulnerability may allow a remote attacker to ru

CVE-2021-21351 CRITICAL POC
9.1 Mar 23

XStream is a Java library to serialize objects to XML and back again. Rated critical severity (CVSS 9.1), this vulnerabi

CVE-2021-21346 CRITICAL POC
9.8 Mar 23

XStream is a Java library to serialize objects to XML and back again. Rated critical severity (CVSS 9.8), this vulnerabi

CVE-2021-21344 CRITICAL POC
9.8 Mar 23

XStream is a Java library to serialize objects to XML and back again. Rated critical severity (CVSS 9.8), this vulnerabi

CVE-2021-21345 CRITICAL POC
9.9 Mar 23

XStream is a Java library to serialize objects to XML and back again. Rated critical severity (CVSS 9.9), this vulnerabi

CVE-2021-29505 HIGH POC
8.8 May 28

XStream is software for serializing Java objects to XML and back again. Rated high severity (CVSS 8.8), this vulnerabili

CVE-2020-26258 HIGH POC
7.7 Dec 16

XStream is a Java library to serialize objects to XML and back again. Rated high severity (CVSS 7.7), this vulnerability

CVE-2021-21341 HIGH POC
7.5 Mar 23

XStream is a Java library to serialize objects to XML and back again. Rated high severity (CVSS 7.5), this vulnerability

CVE-2021-21342 CRITICAL POC
9.1 Mar 23

XStream is a Java library to serialize objects to XML and back again. Rated critical severity (CVSS 9.1), this vulnerabi

CVE-2021-21349 HIGH POC
8.6 Mar 23

XStream is a Java library to serialize objects to XML and back again. Rated high severity (CVSS 8.6), this vulnerability

CVE-2021-21343 HIGH POC
7.5 Mar 23

XStream is a Java library to serialize objects to XML and back again. Rated high severity (CVSS 7.5), this vulnerability

CVE-2021-21350 CRITICAL POC
9.8 Mar 23

XStream is a Java library to serialize objects to XML and back again. Rated critical severity (CVSS 9.8), this vulnerabi

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