CVE-2021-21346

HIGHNVD 6.18.5▲
EchelonGraph scoreHIGH confidence

Score elevated to 8.5 because EPSS predicts 76% probability of exploitation within the next 30 days (top 0.5% of all CVEs). NVD baseline CVSS 6.1 retained for reference. Confidence: see factors.

Triggered by: EPSS exploit prediction ≥85%
Sources: epss, nvd
Elevated
8.5EG
EchelonGraph verdictPatch this weekExploitation is likely or a public exploit exists.
  • High exploitation likelihood — EPSS 76%
CISA-KEV: Not listedEPSS PROB: 76%CVSS: 6.1Exploit: 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 1.4.16, there is a vulnerability which may allow a remote attacker to load and execute arbitrary code from a remote host only by manipulating the processed input stream. No user is affected, who followed the recommendation to setup XStream's security framework with a whitelist limited to the minimal required types. If you rely on XStream's default blacklist of the Security Framework, you will have to use at least version 1.4.16.

CVSS v3
6.1
EG Score
8.5(high)
EG Risk
73(Track)
EG Risk 73/100SSVC: 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
Severity85% × 45%
Exploitation76% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
76%
EPSS %ILE
99%
KEV
Not listed

Published

March 23, 2021

Last Modified

May 23, 2025

References (30)

Vendor Advisories for CVE-2021-21346(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(6)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntulibxstream-java (1.4.15-1ubuntu0.1) @ hirsute2026-05-26ubuntu
ubuntulibxstream-java (1.4.8-1ubuntu0.1+esm3) @ xenial2026-05-26ubuntu
redhatxstream2021-12-14redhat
redhatpatch2021-12-02redhat
redhatpatch2021-11-23redhat
redhatxstream-0:1.3.1-13.el7_92021-04-26redhat

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 (40 versions)1.4.16—

Weakness Classification(2)

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

Additional Vendor Advisories

(8)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 6× in last 7d / 23× 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 14:52 UTCEPSS rescore
  2. 2026-07-24 14:15 UTCEPSS rescore
  3. 2026-07-23 01:57 UTCEG score recompute▲ 2.40
  4. 2026-07-22 22:43 UTCEG score recompute
  5. 2026-07-22 14:05 UTCEPSS rescore
  6. 2026-07-20 17:04 UTCEPSS rescore
  7. 2026-07-18 23:59 UTCOSV refresh
  8. 2026-07-15 16:55 UTCEPSS rescore
  9. 2026-07-15 16:55 UTCEPSS rescore
  10. 2026-07-12 05:44 UTCEPSS rescore
  11. 2026-07-12 05:44 UTCEPSS rescore
  12. 2026-07-11 08:25 UTCEPSS rescore
  13. 2026-07-07 13:43 UTCEPSS rescore
  14. 2026-07-05 02:28 UTCEPSS rescore
  15. 2026-07-05 02:28 UTCEPSS rescore
  16. 2026-07-01 15:03 UTCEPSS rescore
  17. 2026-07-01 06:48 UTCOSV refresh
  18. 2026-06-30 23:20 UTCEPSS rescore
  19. 2026-06-30 23:20 UTCEPSS rescore
  20. 2026-06-29 14:04 UTCEPSS rescore
  21. 2026-06-29 14:04 UTCEPSS rescore
  22. 2026-06-28 04:54 UTCEPSS rescore
  23. 2026-06-28 04:54 UTCEPSS rescore
  24. 2026-06-27 03:06 UTCEPSS rescore
  25. 2026-06-27 03:06 UTCEPSS rescore
Show 51 more
  1. 2026-06-25 13:48 UTCEPSS rescore
  2. 2026-06-25 13:48 UTCEPSS rescore
  3. 2026-06-24 14:03 UTCEPSS rescore
  4. 2026-06-24 14:03 UTCEPSS rescore
  5. 2026-06-23 21:31 UTCEPSS rescore
  6. 2026-06-23 21:31 UTCEPSS rescore
  7. 2026-06-21 01:58 UTCEPSS rescore
  8. 2026-06-21 01:57 UTCEPSS rescore
  9. 2026-06-16 17:50 UTCEPSS rescore
  10. 2026-06-15 17:46 UTCEPSS rescore
  11. 2026-06-14 23:15 UTCEPSS rescore
  12. 2026-06-13 22:58 UTCEPSS rescore
  13. 2026-06-13 11:13 UTCOSV refresh
  14. 2026-06-12 23:10 UTCEPSS rescore
  15. 2026-06-12 23:10 UTCEPSS rescore
  16. 2026-06-11 13:58 UTCEPSS rescore
  17. 2026-06-10 22:16 UTCEPSS rescore
  18. 2026-06-10 22:16 UTCEPSS rescore
  19. 2026-06-10 13:20 UTCEPSS rescore
  20. 2026-06-08 14:15 UTCEPSS rescore
  21. 2026-06-08 14:15 UTCEPSS rescore
  22. 2026-06-07 15:23 UTCEPSS rescore
  23. 2026-06-07 15:23 UTCEPSS rescore
  24. 2026-06-06 13:46 UTCEPSS rescore
  25. 2026-06-06 13:46 UTCEPSS rescore
  26. 2026-06-06 13:46 UTCEPSS rescore
  27. 2026-06-05 22:45 UTCEPSS rescore
  28. 2026-06-05 22:45 UTCEPSS rescore
  29. 2026-06-05 06:09 UTCEPSS rescore
  30. 2026-06-05 06:09 UTCEPSS rescore
  31. 2026-06-05 06:08 UTCEPSS rescore
  32. 2026-06-04 13:10 UTCEPSS rescore
  33. 2026-06-02 20:11 UTCEPSS rescore
  34. 2026-06-02 20:11 UTCEPSS rescore
  35. 2026-06-01 13:50 UTCEPSS rescore
  36. 2026-06-01 13:50 UTCEPSS rescore
  37. 2026-05-31 22:29 UTCEPSS rescore
  38. 2026-05-31 22:29 UTCEPSS rescore
  39. 2026-05-31 00:15 UTCEPSS rescore
  40. 2026-05-31 00:15 UTCEPSS rescore
  41. 2026-05-29 13:42 UTCEPSS rescore
  42. 2026-05-28 13:43 UTCEPSS rescore
  43. 2026-05-28 13:43 UTCEPSS rescore
  44. 2026-05-27 13:39 UTCEPSS rescore
  45. 2026-05-26 19:33 UTCEG score recompute
  46. 2026-05-26 19:33 UTCVendor advisory
  47. 2026-05-26 13:42 UTCEPSS rescore
  48. 2026-05-26 13:42 UTCEPSS rescore
  49. 2026-05-26 07:17 UTCEPSS rescore
  50. 2026-05-26 07:17 UTCEPSS rescore
  51. 2026-05-24 16:49 UTCEPSS rescore

Frequently asked(5)

What is CVE-2021-21346?
CVE-2021-21346 is a high vulnerability published on March 23, 2021. XStream is a Java library to serialize objects to XML and back again. In XStream before version 1.4.16, there is a vulnerability which may allow a remote attacker to load and execute arbitrary code from a remote host only by manipulating the processed input stream. No user is affected, who followed…
When was CVE-2021-21346 disclosed?
CVE-2021-21346 was first published in the National Vulnerability Database on March 23, 2021, 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-2021-21346 actively exploited?
CVE-2021-21346 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 76% probability of exploitation in the next 30 days, which ranks it in the top 0.5% of all scored CVEs.
What is the CVSS score of CVE-2021-21346?
CVE-2021-21346 has a CVSS v3 base score of 6.1 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 8.5.
How do I remediate CVE-2021-21346?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-21346, 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

See which npm, PyPI, Go, and Maven packages are affected by CVE-2021-21346

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