CVE-2020-26258

MEDIUMNVD 6.36.3
EchelonGraph scoreLOW confidence

This medium-severity CVE scores 6.3 under NVD CVSS v3. EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: nvd
Elevated
6.3
EchelonGraph verdictPatch this weekExploitation is likely or a public exploit exists.
  • High exploitation likelihood — EPSS 82%
CISA-KEV: Not listedEPSS: 82%CVSS: 6.3Exploit: NoneExposed: 0

A fix is available — apply it.

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.

CVSS v3
6.3
EG Score
6.3(low)
EPSS
99.6%
KEV
Not listed

Published

December 16, 2020

Last Modified

May 23, 2025

References (18)

Patch Availability(6)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntulibxstream-java (1.4.11.1-1ubuntu0.1) @ focal2026-05-23ubuntu
ubuntulibxstream-java (1.4.11.1-2ubuntu0.1) @ groovy2026-05-23ubuntu
ubuntulibxstream-java (1.4.8-1ubuntu0.1+esm3) @ xenial2026-05-23ubuntu
redhatpatch2021-11-23redhat
redhatpatch2021-08-18redhat
redhatxstream2021-08-11redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(1 across 1 ecosystem)
Maven(1)
PackageVulnerable rangeFixed inDependents
com.thoughtworks.xstream:xstream0.1 ... 1.4.9 (39 versions)1.4.15—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

All Vendor Advisories

(9)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 3× in last 7d / 19× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-22 14:05 UTCEPSS rescore
  2. 2026-07-20 17:04 UTCEPSS rescore
  3. 2026-07-20 17:04 UTCEPSS rescore
  4. 2026-07-15 16:55 UTCEPSS rescore
  5. 2026-07-15 16:55 UTCEPSS rescore
  6. 2026-07-15 01:57 UTCEPSS rescore
  7. 2026-07-12 21:37 UTCOSV refresh
  8. 2026-07-12 05:44 UTCEPSS rescore
  9. 2026-07-09 19:07 UTCEPSS rescore
  10. 2026-07-06 02:21 UTCEPSS rescore
  11. 2026-07-06 02:21 UTCEPSS rescore
  12. 2026-07-04 06:29 UTCEPSS rescore
  13. 2026-07-04 06:29 UTCEPSS rescore
  14. 2026-06-28 04:54 UTCEPSS rescore
  15. 2026-06-28 04:54 UTCEPSS rescore
  16. 2026-06-25 13:48 UTCEPSS rescore
  17. 2026-06-24 07:20 UTCOSV refresh
  18. 2026-06-23 21:31 UTCEPSS rescore
  19. 2026-06-23 21:31 UTCEPSS rescore
  20. 2026-06-21 14:54 UTCEPSS rescore
  21. 2026-06-21 14:54 UTCEPSS rescore
  22. 2026-06-21 01:57 UTCEPSS rescore
  23. 2026-06-17 17:50 UTCEPSS rescore
  24. 2026-06-15 17:46 UTCEPSS rescore
  25. 2026-06-13 22:58 UTCEPSS rescore
Show 14 more
  1. 2026-06-10 22:16 UTCEPSS rescore
  2. 2026-06-08 14:15 UTCEPSS rescore
  3. 2026-06-07 10:59 UTCOSV refresh
  4. 2026-06-04 13:10 UTCEPSS rescore
  5. 2026-06-04 13:10 UTCEPSS rescore
  6. 2026-05-28 13:43 UTCEPSS rescore
  7. 2026-05-28 13:43 UTCEPSS rescore
  8. 2026-05-27 13:39 UTCEPSS rescore
  9. 2026-05-26 13:42 UTCEPSS rescore
  10. 2026-05-26 13:42 UTCEPSS rescore
  11. 2026-05-26 07:17 UTCEPSS rescore
  12. 2026-05-26 07:17 UTCEPSS rescore
  13. 2026-05-23 04:07 UTCEG score recompute
  14. 2026-05-23 04:07 UTCVendor advisory

Publicly available exploits

(1 reference)

Working exploit code is in the public domain. Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • Nucleihttp/cves/2020/CVE-2020-26258.yaml
    First seen Jan 1, 2020

    XStream <1.4.15 - Server-Side Request Forgery

    Open source ↗

Frequently asked(5)

What is CVE-2020-26258?
CVE-2020-26258 is a medium vulnerability published on December 16, 2020. 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…
When was CVE-2020-26258 disclosed?
CVE-2020-26258 was first published in the National Vulnerability Database on December 16, 2020, with the most recent update on May 23, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2020-26258 actively exploited?
CVE-2020-26258 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 99.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2020-26258?
CVE-2020-26258 has a CVSS v3 base score of 6.3 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2020-26258?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2020-26258, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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