CVE-2021-21347

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 14% (96th percentile of EPSS-scored CVEs). 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
Trending — 4 sources updated this weekElevated
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 14%CVSS: 9.8Exploit: Elevated riskExposed services: Not assessed

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
9.8
EG Score
9.8CRITICALmedium confidence
EG Risk
75
EG Risk 75/100CISA SSVC

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
Severity98% × 45%
Exploitation40% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
14%
EPSS %ILE
96th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

March 23, 2021

Last Modified

October 7, 2026

Advisory Details (12)

Auto-updated Oct 7, 2026
Patch available. Sources: github.
generic

[SECURITY] [DSA 5004-1] libxstream-java security update

https://www.debian.org/security/2021/dsa-5004
generic

NetApp Product Security

https://security.netapp.com/advisory/ntap-20210430-0002/
generic

[SECURITY] Fedora 34 Update: xstream-1.4.18-2.fc34 - package-announce - Fedora mailing-lists

https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QGXIU3YDPG6OGTDHMBLAFN7BPBERXREB/
generic

[SECURITY] Fedora 35 Update: xstream-1.4.18-2.fc35 - package-announce - Fedora mailing-lists

https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PVPHZA7VW2RRSDCOIPP2W6O5ND254TU7/
generic

[SECURITY] Fedora 33 Update: xstream-1.4.18-2.fc33 - package-announce - Fedora mailing-lists

https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/22KVR6B5IZP3BGQ3HPWIO2FWWCKT3DHP/
genericMentions a patch (unverified)

[SECURITY] [DLA 2616-1] libxstream-java security update

https://lists.debian.org/debian-lts-announce/2021/04/msg00002.html
generic

Pony Mail

https://lists.apache.org/thread.html/r9ac71b047767205aa22e3a08cb33f3e0586de6b2fac48b425c6e16b0%40%3Cdev.jmeter.apache.org%3E
generic

Pony Mail

https://lists.apache.org/thread.html/r8244fd0831db894d5e89911ded9c72196d395a90ae655414d23ed0dd%40%3Cusers.activemq.apache.org%3E
githubMentions a patch (unverified)

XStream is vulnerable to an Arbitrary Code Execution attack · Advisory · x-stream/xstream · GitHub

https://github.com/x-stream/xstream/security/advisories/GHSA-qpfq-ph7r-qv6f
generic

XStream - Change History

http://x-stream.github.io/changes.html#1.4.16
generic

XStream - CVE-2021-21347

https://x-stream.github.io/CVE-2021-21347.html
generic

XStream - Security Aspects

https://x-stream.github.io/security.html#workaround

Vendor Advisories for CVE-2021-21347(5)

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 / EcosystemFix (by version range) / PatchReleasedSource
ubuntulibxstream-java (1.4.8-1ubuntu0.1+esm3) @ xenial2026-10-07ubuntu
ubuntulibxstream-java (1.4.15-1ubuntu0.1) @ hirsute2026-10-07ubuntu
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

(6 across 6 ecosystems)
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
libxstream-java—
  • every version up to 1.4.15-2: fixed in 1.4.15-2
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
libxstream-java—
  • every version up to 1.4.15-2: fixed in 1.4.15-2
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
libxstream-java—
  • every version up to 1.4.15-2: fixed in 1.4.15-2
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
libxstream-java—
  • every version up to 1.4.15-2: fixed in 1.4.15-2
—
Debian:9(1)
PackageVulnerable rangeFix by version rangeDependents
libxstream-java1.4.10-1 ... 1.4.9-2+deb9u1 (6 versions)
  • every version up to 1.4.11.1-1+deb9u2: fixed in 1.4.11.1-1+deb9u2
—
Maven(1)
PackageVulnerable rangeFix by version rangeDependents
com.thoughtworks.xstream:xstream0.1 ... 1.4.9 (40 versions)
  • every version up to 1.4.16: fixed in 1.4.16
—

Weakness Classification(2)

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

Additional Vendor Advisories

(4)

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 12× in last 7d / 35× 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.

Showing the most recent 100 of 169 total refreshes for this CVE.

  1. 2026-10-09 20:04 UTCEPSS rescore
  2. 2026-10-08 16:39 UTCEPSS rescore
  3. 2026-10-07 23:44 UTCEPSS rescore
  4. 2026-10-07 19:28 UTCEG score recompute▲ 3.70
  5. 2026-10-07 19:28 UTCVendor advisory
  6. 2026-10-07 19:19 UTCNVD updateCVSS v3 → 9.8 · severity → CRITICAL
  7. 2026-10-07 18:29 UTCEG score recompute
  8. 2026-10-07 18:29 UTCVendor advisory
  9. 2026-10-06 15:13 UTCEPSS rescore
  10. 2026-10-05 17:40 UTCEPSS rescore
  11. 2026-10-03 14:22 UTCEPSS rescore
  12. 2026-10-03 14:22 UTCEPSS rescore
  13. 2026-10-02 16:22 UTCEPSS rescore
  14. 2026-10-01 19:46 UTCEPSS rescore
  15. 2026-09-30 15:29 UTCEG score recompute
  16. 2026-09-30 15:00 UTCEPSS rescore
  17. 2026-09-28 13:47 UTCEPSS rescore
  18. 2026-09-27 13:41 UTCEPSS rescore
  19. 2026-09-26 15:54 UTCEPSS rescore
  20. 2026-09-26 15:54 UTCEPSS rescore
  21. 2026-09-26 05:55 UTCOSV refresh
  22. 2026-09-26 00:21 UTCEPSS rescore
  23. 2026-09-24 14:00 UTCEPSS rescore
  24. 2026-09-24 14:00 UTCEPSS rescore
  25. 2026-09-23 13:44 UTCEPSS rescore
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  1. 2026-09-22 14:44 UTCEPSS rescore
  2. 2026-09-21 20:28 UTCEPSS rescore
  3. 2026-09-19 15:37 UTCEPSS rescore
  4. 2026-09-18 19:23 UTCEPSS rescore
  5. 2026-09-17 19:23 UTCEPSS rescore
  6. 2026-09-16 14:05 UTCEPSS rescore
  7. 2026-09-16 14:04 UTCEPSS rescore
  8. 2026-09-15 03:06 UTCEPSS rescore
  9. 2026-09-12 14:57 UTCEPSS rescore
  10. 2026-09-11 09:33 UTCEPSS rescore
  11. 2026-09-10 09:29 UTCEPSS rescore
  12. 2026-09-08 21:56 UTCEPSS rescore
  13. 2026-09-07 15:58 UTCEPSS rescore
  14. 2026-09-06 20:31 UTCOSV refresh
  15. 2026-09-06 13:44 UTCEPSS rescore
  16. 2026-09-06 13:44 UTCEPSS rescore
  17. 2026-09-05 15:25 UTCEPSS rescore
  18. 2026-09-04 13:57 UTCEPSS rescore
  19. 2026-09-04 05:03 UTCEPSS rescore
  20. 2026-09-02 14:08 UTCEPSS rescore
  21. 2026-09-01 13:50 UTCEPSS rescore
  22. 2026-09-01 03:32 UTCEPSS rescore
  23. 2026-08-30 19:14 UTCEPSS rescore
  24. 2026-08-30 01:19 UTCEPSS rescore
  25. 2026-08-28 21:37 UTCEPSS rescore
  26. 2026-08-27 14:22 UTCEPSS rescore
  27. 2026-08-26 14:42 UTCEPSS rescore
  28. 2026-08-25 13:45 UTCEPSS rescore
  29. 2026-08-23 00:16 UTCEPSS rescore
  30. 2026-08-21 23:46 UTCEPSS rescore
  31. 2026-08-20 22:52 UTCEPSS rescore
  32. 2026-08-20 06:34 UTCOSV refresh
  33. 2026-08-19 17:01 UTCEPSS rescore
  34. 2026-08-18 13:45 UTCEPSS rescore
  35. 2026-08-16 14:52 UTCEPSS rescore
  36. 2026-08-16 02:11 UTCEPSS rescore
  37. 2026-08-15 01:27 UTCEPSS rescore
  38. 2026-08-13 21:57 UTCEPSS rescore
  39. 2026-08-12 13:47 UTCEPSS rescore
  40. 2026-08-11 13:38 UTCEPSS rescore
  41. 2026-08-09 13:43 UTCEPSS rescore
  42. 2026-08-08 16:33 UTCEPSS rescore
  43. 2026-08-07 16:23 UTCEPSS rescore
  44. 2026-08-06 13:43 UTCEPSS rescore
  45. 2026-08-05 19:14 UTCEPSS rescore
  46. 2026-08-05 01:40 UTCOSV refresh
  47. 2026-08-04 15:06 UTCEPSS rescore
  48. 2026-08-04 10:34 UTCEPSS rescore
  49. 2026-08-01 04:12 UTCEPSS rescore
  50. 2026-07-30 16:25 UTCEPSS rescore
  51. 2026-07-26 14:52 UTCEPSS rescore
  52. 2026-07-25 14:15 UTCEPSS rescore
  53. 2026-07-24 14:15 UTCEPSS rescore
  54. 2026-07-23 14:15 UTCEPSS rescore
  55. 2026-07-23 01:57 UTCEG score recompute
  56. 2026-07-22 22:43 UTCEG score recompute
  57. 2026-07-22 14:05 UTCEPSS rescore
  58. 2026-07-21 15:22 UTCEPSS rescore
  59. 2026-07-21 15:22 UTCEPSS rescore
  60. 2026-07-20 17:04 UTCEPSS rescore
  61. 2026-07-19 02:26 UTCEPSS rescore
  62. 2026-07-18 23:59 UTCOSV refresh
  63. 2026-07-18 10:02 UTCEPSS rescore
  64. 2026-07-16 17:00 UTCEPSS rescore
  65. 2026-07-15 16:55 UTCEPSS rescore
  66. 2026-07-15 16:55 UTCEPSS rescore
  67. 2026-07-13 22:27 UTCEPSS rescore
  68. 2026-07-13 22:27 UTCEPSS rescore
  69. 2026-07-12 05:44 UTCEPSS rescore
  70. 2026-07-12 05:44 UTCEPSS rescore
  71. 2026-07-11 08:25 UTCEPSS rescore
  72. 2026-07-09 19:07 UTCEPSS rescore
  73. 2026-07-08 15:12 UTCEPSS rescore
  74. 2026-07-07 13:43 UTCEPSS rescore
  75. 2026-07-05 02:28 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2021-21347?
CVE-2021-21347 is a critical 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-2021-21347 disclosed?
CVE-2021-21347 was first published on March 23, 2021, with the most recent update on October 7, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-21347 actively exploited?
CVE-2021-21347 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 14% probability of exploitation in the next 30 days (96th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2021-21347?
CVE-2021-21347 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2021-21347?
A fix for CVE-2021-21347 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2021-21347 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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