---
id: CVE-2020-26258
title: XStream is a Java library to serialize objects to XML and back again
summary: >-
  XStream is a Java library to serialize objects to XML and back again. In
  XStream before version 1.4.15, a Server-Side Forgery Request vulnerability can
  be activated when unmarshalling. The vulnerability may allow a remote attacker
  to req…
severity: medium
cvss: 6.3
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N'
cwe:
  - CWE-918
vendor: apache
product: struts
affected:
  - struts < 6.0.0
  - xstream < 1.4.15
  - debian_linux = 9.0
  - debian_linux = 10.0
  - fedora = 33
  - fedora = 34
  - fedora = 35
patched:
  - struts 6.0.0
  - xstream 1.4.15
published: '2020-12-16'
updated: '2026-10-07'
sourceUpdated: '2026-10-07T19:17:17.510'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2020-26258'
references:
  - url: >-
      https://github.com/x-stream/xstream/security/advisories/GHSA-4cch-wxpw-8p28
    label: security-advisories@github.com
  - url: >-
      https://lists.apache.org/thread.html/r97993e3d78e1f5389b7b172ba9f308440830ce5f051ee62714a0aa34@%3Ccommits.struts.apache.org%3E
    label: security-advisories@github.com
  - url: 'https://lists.debian.org/debian-lts-announce/2020/12/msg00042.html'
    label: security-advisories@github.com
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/22KVR6B5IZP3BGQ3HPWIO2FWWCKT3DHP
    label: security-advisories@github.com
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/PVPHZA7VW2RRSDCOIPP2W6O5ND254TU7
    label: security-advisories@github.com
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QGXIU3YDPG6OGTDHMBLAFN7BPBERXREB
    label: security-advisories@github.com
  - url: 'https://security.netapp.com/advisory/ntap-20210409-0005'
    label: security-advisories@github.com
  - url: 'https://www.debian.org/security/2021/dsa-4828'
    label: security-advisories@github.com
  - url: 'https://x-stream.github.io/CVE-2020-26258.html'
    label: security-advisories@github.com
  - url: >-
      https://github.com/x-stream/xstream/security/advisories/GHSA-4cch-wxpw-8p28
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://lists.apache.org/thread.html/r97993e3d78e1f5389b7b172ba9f308440830ce5f051ee62714a0aa34%40%3Ccommits.struts.apache.org%3E
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://lists.debian.org/debian-lts-announce/2020/12/msg00042.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/22KVR6B5IZP3BGQ3HPWIO2FWWCKT3DHP/
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PVPHZA7VW2RRSDCOIPP2W6O5ND254TU7/
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QGXIU3YDPG6OGTDHMBLAFN7BPBERXREB/
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://security.netapp.com/advisory/ntap-20210409-0005/'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://www.debian.org/security/2021/dsa-4828'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://x-stream.github.io/CVE-2020-26258.html'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
  - cve.org
  - exploit-available
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-07T18:41:22.362836Z'
epss: 0.81817
epssPercentile: 0.9964
exploits:
  github: 2
  githubRepos:
    - 'https://github.com/Al1ex/CVE-2020-26258'
    - 'https://github.com/cuijiung/xstream-CVE-2020-26258'
  nuclei:
    - CVE-2020-26258
  checkedAt: '2026-10-07T19:44:51.103Z'
exploitAvailable: true
ingestedAt: '2026-10-07T19:44:15.639Z'
---

## Overview

XStream is a Java library to serialize objects to XML and back again. In XStream before version 1.4.15, a Server-Side Forgery Request vulnerability can be activated when unmarshalling. The vulnerability may allow a remote attacker to request data from internal resources that are not publicly available 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 if 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

- `struts < 6.0.0`
- `xstream < 1.4.15`
- `debian_linux = 9.0`
- `debian_linux = 10.0`
- `fedora = 33`
- `fedora = 34`
- `fedora = 35`

## Remediation

Upgrade past the affected range:

- `struts 6.0.0`
- `xstream 1.4.15`