CVE-2020-26259: Xstream XStream Vulnerable To An Arbitrary Vulnerability

MODERATE
Advisory Identifier: GHSA-jfvx-7wrx-43fh
CVSS 6.8
CWE-78
Published
Advisory Summary

CVE-2020-26259 is a MODERATE (CVSS 6.8) xstream vulnerable to an arbitrary vulnerability (CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')) affecting Xstream libraries in the Maven ecosystem. The issue involves xstream vulnerable to an arbitrary file deletion on the local host when unmarshalling. Remediation is available by upgrading affected packages to version 1.4.15.

CVE-2020-26259 at a Glance

CVE Identifier CVE-2020-26259
GHSA Identifier GHSA-jfvx-7wrx-43fh
Severity MODERATE
CVSS v3.1 Base Score 6.8
CWE Classification CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
Affected Product Xstream
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 6.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Changed (S:C)
Confidentiality None (C:N)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2020-26259

To remediate this vulnerability, upgrade all affected Xstream dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

com.thoughtworks.xstream:xstream fixed: 1.4.15
<dependency>
    <groupId>com.thoughtworks.xstream</groupId>
    <artifactId>xstream</artifactId>
    <version>1.4.15</version>
</dependency>
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release:

mvn dependency:tree -Dincludes=com.thoughtworks.xstream

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2020-26259, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=com.thoughtworks.xstream

Analyze the terminal output to locate any version of Xstream in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.4.15), your application is affected.

Note: The mvn dependency:tree -Dincludes=com.thoughtworks.xstream command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection'), where the product constructs all or part of an os command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended os command when it is sent to a downstream component. In Xstream, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact 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. ### Patches If you rely on XStream's default blacklist of the [Security Framework](https://x-stream.github.io/security.html#framework), you will have to use at least version 1.4.15. ### Workarounds The reported vulnerability does only exist with a JAX-WS runtime on the classpath. 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 insist to use XStream default blacklist - despite that clear recommendation - can use a workaround depending on their version in use. Users of XStream 1.4.14 can simply add two lines to XStream's setup code: ```Java xstream.denyTypes(new String[]{ "jdk.nashorn.internal.objects.NativeString" }); xstream.denyTypesByRegExp(new String[]{ ".*\\.ReadAllStream\\$FileStream" }); ``` Users of XStream 1.4.14 to 1.4.13 can simply add three lines to XStream's setup code: ```Java xstream.denyTypes(new String[]{ "javax.imageio.ImageIO$ContainsFilter", "jdk.nashorn.internal.objects.NativeString" }); xstream.denyTypes(new Class[]{ java.lang.ProcessBuilder.class }); xstream.denyTypesByRegExp(new String[]{ ".*\\.ReadAllStream\\$FileStream" }); ``` Users of XStream 1.4.12 to 1.4.7 who want to use XStream with a black list will have to setup such a list from scratch and deny at least the following types: _javax.imageio.ImageIO$ContainsFilter_, _java.beans.EventHandler_, _java.lang.ProcessBuilder_, _jdk.nashorn.internal.objects.NativeString.class_, _java.lang.Void_ and _void_ and deny several types by name pattern. ```Java xstream.denyTypes(new String[]{ "javax.imageio.ImageIO$ContainsFilter", "jdk.nashorn.internal.objects.NativeString" }); xstream.denyTypes(new Class[]{ java.lang.ProcessBuilder.class, "jdk.nashorn.internal.objects.NativeString", java.beans.EventHandler.class, java.lang.ProcessBuilder.class, java.lang.Void.class, void.class }); xstream.denyTypesByRegExp(new String[]{ ".*\\$LazyIterator", "javax\\.crypto\\..*", ".*\\.ReadAllStream\\$FileStream" }); ``` Users of XStream 1.4.6 or below can register an own converter to prevent the unmarshalling of the currently know critical types of the Java runtime. It is in fact an updated version of the workaround for CVE-2013-7285: ```Java xstream.registerConverter(new Converter() { public boolean canConvert(Class type) { return type != null && (type == java.beans.EventHandler.class || type == java.lang.ProcessBuilder.class || type.getName().equals("javax.imageio.ImageIO$ContainsFilter") || type.getName().equals("jdk.nashorn.internal.objects.NativeString") || type == java.lang.Void.class || void.class || Proxy.isProxy(type)) || type.getName().startsWith("javax.crypto.") || type.getName().endsWith("$LazyIterator") || type.getName().endsWith(".ReadAllStream$FileStream")); } public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) { throw new ConversionException("Unsupported type due to security reasons."); } public void marshal(Object source, HierarchicalStreamWriter writer, MarshallingContext context) { throw new ConversionException("Unsupported type due to security reasons."); } }, XStream.PRIORITY_LOW); ``` ### For more information If you have any questions or comments about this advisory: * Open an issue in [XStream](https://github.com/x-stream/xstream/issues) * Contact us at [XStream Google Group](https://groups.google.com/group/xstream-user)

CVE-2020-26259 Affected Xstream Versions

1 component(s)
Fixed Versions:
1.4.15
Product / Package Ecosystem Affected Versions Fixed Version
com.thoughtworks.xstream:xstream
Maven
< 1.4.15
1.4.15

References

Frequently Asked Questions

What is CVE-2020-26259?
CVE-2020-26259 is a security vulnerability in Xstream involving XStream vulnerable to an Arbitrary File Deletion on the local host when unmarshalling under CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection').
Which Xstream versions are affected?
Affected versions include releases prior to 1.4.15 across affected packages: com.thoughtworks.xstream:xstream.
What version fixes CVE-2020-26259?
Upgrading to 1.4.15 (or the latest patched release for your respective branch) resolves the vulnerability.
Is xstream affected?
Yes, com.thoughtworks.xstream:xstream is affected in releases prior to 1.4.15. Upgrade your dependency to 1.4.15 or later.
What is the CVSS score of CVE-2020-26259?
CVE-2020-26259 has a CVSS v3.1 base score of 6.8 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N.
What CWE is associated with CVE-2020-26259?
CVE-2020-26259 is classified under CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection') (The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.).
How can I check Maven dependencies for CVE-2020-26259?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=com.thoughtworks.xstream'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-jfvx-7wrx-43fh",
  "modified" : "2021-11-18T15:24:49Z",
  "published" : "2020-12-21T16:28:26Z",
  "aliases" : [ "CVE-2020-26259" ],
  "summary" : "XStream vulnerable to an Arbitrary File Deletion on the local host when unmarshalling",
  "details" : "### Impact\nThe 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.\n\n### Patches\nIf you rely on XStream's default blacklist of the [Security Framework](https://x-stream.github.io/security.html#framework), you will have to use at least version 1.4.15.\n\n### Workarounds\nThe reported vulnerability does only exist with a JAX-WS runtime on the classpath.\n\nNo 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.\n\nUsers of XStream 1.4.14 or below who still insist to use XStream default blacklist - despite that clear recommendation - can use a workaround depending on their version in use.\n\nUsers of XStream 1.4.14 can simply add two lines to XStream's setup code:\n```Java\nxstream.denyTypes(new String[]{ \"jdk.nashorn.internal.objects.NativeString\" });\nxstream.denyTypesByRegExp(new String[]{ \".*\\\\.ReadAllStream\\\\$FileStream\" });\n```\n\nUsers of XStream 1.4.14 to 1.4.13 can simply add three lines to XStream's setup code:\n```Java\nxstream.denyTypes(new String[]{ \"javax.imageio.ImageIO$ContainsFilter\", \"jdk.nashorn.internal.objects.NativeString\" });\nxstream.denyTypes(new Class[]{ java.lang.ProcessBuilder.class });\nxstream.denyTypesByRegExp(new String[]{ \".*\\\\.ReadAllStream\\\\$FileStream\" });\n```\nUsers of XStream 1.4.12 to 1.4.7 who want to use XStream with a black list will have to setup such a list from scratch and deny at least the following types: _javax.imageio.ImageIO$ContainsFilter_, _java.beans.EventHandler_, _java.lang.ProcessBuilder_, _jdk.nashorn.internal.objects.NativeString.class_, _java.lang.Void_ and _void_ and deny several types by name pattern.\n```Java\nxstream.denyTypes(new String[]{ \"javax.imageio.ImageIO$ContainsFilter\", \"jdk.nashorn.internal.objects.NativeString\" });\nxstream.denyTypes(new Class[]{ java.lang.ProcessBuilder.class, \"jdk.nashorn.internal.objects.NativeString\", java.beans.EventHandler.class, java.lang.ProcessBuilder.class, java.lang.Void.class, void.class });\nxstream.denyTypesByRegExp(new String[]{ \".*\\\\$LazyIterator\", \"javax\\\\.crypto\\\\..*\", \".*\\\\.ReadAllStream\\\\$FileStream\" });\n```\nUsers of XStream 1.4.6 or below can register an own converter to prevent the unmarshalling of the currently know critical types of the Java runtime. It is in fact an updated version of the workaround for CVE-2013-7285:\n```Java\nxstream.registerConverter(new Converter() {\n  public boolean canConvert(Class type) {\n    return type != null && (type == java.beans.EventHandler.class || type == java.lang.ProcessBuilder.class\n        || type.getName().equals(\"javax.imageio.ImageIO$ContainsFilter\") || type.getName().equals(\"jdk.nashorn.internal.objects.NativeString\")\n        || type == java.lang.Void.class || void.class || Proxy.isProxy(type))\n        || type.getName().startsWith(\"javax.crypto.\") || type.getName().endsWith(\"$LazyIterator\") || type.getName().endsWith(\".ReadAllStream$FileStream\"));\n  }\n\n  public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {\n    throw new ConversionException(\"Unsupported type due to security reasons.\");\n  }\n\n  public void marshal(Object source, HierarchicalStreamWriter writer, MarshallingContext context) {\n    throw new ConversionException(\"Unsupported type due to security reasons.\");\n  }\n}, XStream.PRIORITY_LOW);\n```\n  \n### For more information\nIf you have any questions or comments about this advisory:\n* Open an issue in [XStream](https://github.com/x-stream/xstream/issues)\n* Contact us at [XStream Google Group](https://groups.google.com/group/xstream-user)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "com.thoughtworks.xstream:xstream"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.4.15"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/x-stream/xstream/security/advisories/GHSA-jfvx-7wrx-43fh"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-26259"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/x-stream/xstream"
  }, {
    "type" : "WEB",
    "url" : "https://lists.apache.org/thread.html/r97993e3d78e1f5389b7b172ba9f308440830ce5f051ee62714a0aa34@%3Ccommits.struts.apache.org%3E"
  }, {
    "type" : "WEB",
    "url" : "https://lists.debian.org/debian-lts-announce/2020/12/msg00042.html"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/22KVR6B5IZP3BGQ3HPWIO2FWWCKT3DHP"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/PVPHZA7VW2RRSDCOIPP2W6O5ND254TU7"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QGXIU3YDPG6OGTDHMBLAFN7BPBERXREB"
  }, {
    "type" : "WEB",
    "url" : "https://security.netapp.com/advisory/ntap-20210409-0005"
  }, {
    "type" : "WEB",
    "url" : "https://www.debian.org/security/2021/dsa-4828"
  }, {
    "type" : "WEB",
    "url" : "https://x-stream.github.io/CVE-2020-26259.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-78" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2020-12-21T16:20:55Z",
    "nvd_published_at" : "2020-12-16T01:15:00Z"
  }
}