CVE-2020-26258

HIGHNVD 6.38.8▲
EchelonGraph scoreHIGH confidence

Score elevated to 8.8 because EPSS predicts 82% probability of exploitation within the next 30 days (top 0.4% of all CVEs). NVD baseline CVSS 6.3 retained for reference. Confidence: see factors.

Triggered by: EPSS exploit prediction ≥85%
Sources: epss, nvd
Elevated
8.8EG
EchelonGraph verdictPatch this weekExploitation is likely or a public exploit exists.
  • High exploitation likelihood — EPSS 82%
CISA-KEV: Not listedEPSS PROB: 82%CVSS: 6.3Exploit: Elevated riskExposed: 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
8.8(high)
EG Risk
77(Track)
EG Risk 77/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity88% × 45%
Exploitation82% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
82%
EPSS %ILE
100%
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 7× 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. 2026-07-26 14:51 UTCEPSS rescore
  2. 2026-07-24 14:14 UTCEPSS rescore
  3. 2026-07-23 01:51 UTCEG score recompute▲ 2.50
  4. 2026-07-22 22:37 UTCEG score recompute
  5. 2026-07-22 14:05 UTCEPSS rescore
  6. 2026-07-20 17:04 UTCEPSS rescore
  7. 2026-07-20 17:04 UTCEPSS rescore
  8. 2026-07-15 16:55 UTCEPSS rescore
  9. 2026-07-15 16:55 UTCEPSS rescore
  10. 2026-07-15 01:57 UTCEPSS rescore
  11. 2026-07-12 21:37 UTCOSV refresh
  12. 2026-07-12 05:44 UTCEPSS rescore
  13. 2026-07-09 19:07 UTCEPSS rescore
  14. 2026-07-06 02:21 UTCEPSS rescore
  15. 2026-07-06 02:21 UTCEPSS rescore
  16. 2026-07-04 06:29 UTCEPSS rescore
  17. 2026-07-04 06:29 UTCEPSS rescore
  18. 2026-06-28 04:54 UTCEPSS rescore
  19. 2026-06-28 04:54 UTCEPSS rescore
  20. 2026-06-25 13:48 UTCEPSS rescore
  21. 2026-06-24 07:20 UTCOSV refresh
  22. 2026-06-23 21:31 UTCEPSS rescore
  23. 2026-06-23 21:31 UTCEPSS rescore
  24. 2026-06-21 14:54 UTCEPSS rescore
  25. 2026-06-21 14:54 UTCEPSS rescore
Show 18 more
  1. 2026-06-21 01:57 UTCEPSS rescore
  2. 2026-06-17 17:50 UTCEPSS rescore
  3. 2026-06-15 17:46 UTCEPSS rescore
  4. 2026-06-13 22:58 UTCEPSS rescore
  5. 2026-06-10 22:16 UTCEPSS rescore
  6. 2026-06-08 14:15 UTCEPSS rescore
  7. 2026-06-07 10:59 UTCOSV refresh
  8. 2026-06-04 13:10 UTCEPSS rescore
  9. 2026-06-04 13:10 UTCEPSS rescore
  10. 2026-05-28 13:43 UTCEPSS rescore
  11. 2026-05-28 13:43 UTCEPSS rescore
  12. 2026-05-27 13:39 UTCEPSS rescore
  13. 2026-05-26 13:42 UTCEPSS rescore
  14. 2026-05-26 13:42 UTCEPSS rescore
  15. 2026-05-26 07:17 UTCEPSS rescore
  16. 2026-05-26 07:17 UTCEPSS rescore
  17. 2026-05-23 04:07 UTCEG score recompute
  18. 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 ↗

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2020-26258?
CVE-2020-26258 is a high 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 82% probability of exploitation in the next 30 days, which ranks it in the top 0.4% of all scored CVEs.
What is the CVSS score of CVE-2020-26258?
CVE-2020-26258 has a CVSS v3 base score of 6.3 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 8.8.
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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