CVE-2021-21343

MEDIUMNVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.3 under NVD CVSS v3. EPSS exploit probability: 0.6%, top 30% of all CVEs by exploit prediction. 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: epss, nvd
Elevated
5.3
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 47%CVSS: 5.3Exploit: 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 1.4.16, there is a vulnerability where the processed stream at unmarshalling time contains type information to recreate the formerly written objects. XStream creates therefore new instances based on these type information. An attacker can manipulate the processed input stream and replace or inject objects, that result in the deletion of a file on the local host. 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
5.3
EG Score
5.3(medium)
EPSS
98.7%
KEV
Not listed

Published

March 23, 2021

Last Modified

May 23, 2025

References (30)

Vendor Advisories for CVE-2021-21343(1)

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

Patch Availability(5)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntulibxstream-java (1.4.15-1ubuntu0.1) @ hirsute2026-05-26ubuntu
ubuntulibxstream-java (1.4.7-1ubuntu0.1+esm2) @ trusty2026-05-26ubuntu
redhatxstream2021-12-14redhat
redhatpatch2021-12-02redhat
redhatpatch2021-11-23redhat

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

(7)

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

Frequently asked(5)

What is CVE-2021-21343?
CVE-2021-21343 is a medium 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 where the processed stream at unmarshalling time contains type information to recreate the formerly written objects. XStream creates therefore new instances based on…
When was CVE-2021-21343 disclosed?
CVE-2021-21343 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-2021-21343 actively exploited?
CVE-2021-21343 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 98.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-21343?
CVE-2021-21343 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2021-21343?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-21343, 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-2021-21343

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