Reference page — cumulative record through Thursday, October 8, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2020-26258

CVE-2020-26258HIGH

x-stream xstream — Server-Side Forgery Request can be activated unmarshalling with XStream

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   L   N  C  H  N  N    7.7   .8182   99.6     —

AFFECTED
  Product  Versions    Fixed
  xstream  < 1.4.15 –  —

TIMELINE
  Oct 1   Reserved by GitHub_M
  Dec 16  Published (CNA: GitHub_M)
  Oct 7   EXPLOIT PUBLISHED — CVE-2020-26258 (x-stream xstream). Public exploit reference added.
  Oct 7   RESCORED — CVE-2020-26258 (x-stream xstream). CVSS 6.3 → 7.7 (NVD).

CWE-918 · CNA: GitHub_M · CVSS v3.1 · 14 references · NVD status: Analyzed

Description

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.

Lifecycle

Complete event history — 4 events, chronological
Date	Event	Detail
October 1, 2020	Reserved	Reserved by GitHub_M
December 16, 2020	Published	Published (CNA: GitHub_M)
October 7, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2020-26258 (x-stream xstream). Public exploit reference added.
October 7, 2026	RESCORED	RESCORED — CVE-2020-26258 (x-stream xstream). CVSS 6.3 → 7.7 (NVD).

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
x-stream	xstream	—	< 1.4.15	—

Weaknesses

CWE-918

References (14)

https://github.com/x-stream/xstream/security/advisories/GHSA-4cch-wxpw-8p28 [Mitigation, Third Party Advisory]
https://lists.apache.org/thread.html/r97993e3d78e1f5389b7b172ba9f308440830ce5f051ee62714a0aa34%40%3Ccommits.struts.apache.org%3E [Issue Tracking, Mailing List]
https://lists.apache.org/thread.html/r97993e3d78e1f5389b7b172ba9f308440830ce5f051ee62714a0aa34@%3Ccommits.struts.apache.org%3E [Issue Tracking, Mailing List]
https://lists.debian.org/debian-lts-announce/2020/12/msg00042.html [Mailing List, Third Party Advisory]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/22KVR6B5IZP3BGQ3HPWIO2FWWCKT3DHP/ [Mailing List]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PVPHZA7VW2RRSDCOIPP2W6O5ND254TU7/ [Mailing List]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QGXIU3YDPG6OGTDHMBLAFN7BPBERXREB/ [Mailing List]
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/22KVR6B5IZP3BGQ3HPWIO2FWWCKT3DHP [Mailing List]
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/PVPHZA7VW2RRSDCOIPP2W6O5ND254TU7 [Mailing List]
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QGXIU3YDPG6OGTDHMBLAFN7BPBERXREB [Mailing List]
https://security.netapp.com/advisory/ntap-20210409-0005 [Third Party Advisory]
https://security.netapp.com/advisory/ntap-20210409-0005/ [Third Party Advisory]
https://www.debian.org/security/2021/dsa-4828 [Third Party Advisory]
https://x-stream.github.io/CVE-2020-26258.html [Exploit, Mitigation, Third Party Advisory]

Authoritative record: CVE-2020-26258 at cve.org

Vendors: x-stream

Weaknesses: CWE-918

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2020-26258 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Thursday, October 8, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.