CVE-2021-39140

MEDIUMNVD 6.36.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.3 under NVD CVSS v3. EPSS exploit probability: 5.9% (93rd 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 week
6.3EG
EchelonGraph verdictMonitorRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 5.9%CVSS: 6.3Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

XStream is a simple library to serialize objects to XML and back again. In affected versions this vulnerability may allow a remote attacker to allocate 100% CPU time on the target system depending on CPU type or parallel execution of such a payload resulting in a denial of service 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. XStream 1.4.18 uses no longer a blacklist by default, since it cannot be secured for general purpose.

CVSS v3
6.3
EG Score
6.3MEDIUMmedium confidence
EG Risk
46
EG Risk 46/100

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 (value × EchelonGraph’s weight)
Severity63% × 45%
The EG Score, 6.3 of 10.
Exploitation6% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
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
5.9%
EPSS %ILE
93rd
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track 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 partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

Published

August 23, 2021

Last Modified

October 7, 2026

Advisory Details (8)

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

NetApp Product Security

https://security.netapp.com/advisory/ntap-20210923-0003/
generic

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

https://www.debian.org/security/2021/dsa-5004
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 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 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 2769-1] libxstream-java security update

https://lists.debian.org/debian-lts-announce/2021/09/msg00017.html
generic

XStream - CVE-2021-39140

https://x-stream.github.io/CVE-2021-39140.html
githubMentions a patch (unverified)

XStream can cause a Denial of Service · Advisory · x-stream/xstream · GitHub

https://github.com/x-stream/xstream/security/advisories/GHSA-6wf9-jmg9-vxcc

Vendor Advisories for CVE-2021-39140(6)

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

Patch Availability(4)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntulibxstream-java (1.4.11.1-1+deb10u4build0.18.04.1) @ bionic2026-10-07ubuntu
redhatxstream2022-02-14redhat
redhatpatch2021-11-23redhat
redhatxstream-0:1.3.1-16.el7_92021-10-25redhat

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

(7 across 7 ecosystems)
Debian:10(1)
PackageVulnerable rangeFix by version rangeDependents
libxstream-java1.4.11.1-1, 1.4.11.1-1+deb10u1, 1.4.11.1-1+deb10u2
  • every version up to 1.4.11.1-1+deb10u3: fixed in 1.4.11.1-1+deb10u3
—
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
libxstream-java1.4.15-3
  • every version up to 1.4.15-3+deb11u1: fixed in 1.4.15-3+deb11u1
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
libxstream-java—
  • every version up to 1.4.18-1: fixed in 1.4.18-1
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
libxstream-java—
  • every version up to 1.4.18-1: fixed in 1.4.18-1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
libxstream-java—
  • every version up to 1.4.18-1: fixed in 1.4.18-1
—
Debian:9(1)
PackageVulnerable rangeFix by version rangeDependents
libxstream-java1.4.10-1 ... 1.4.9-2+deb9u1 (8 versions)
  • every version up to 1.4.11.1-1+deb9u4: fixed in 1.4.11.1-1+deb9u4
—
Maven(1)
PackageVulnerable rangeFix by version rangeDependents
com.thoughtworks.xstream:xstream0.1 ... 1.4.9 (42 versions)
  • every version up to 1.4.18: fixed in 1.4.18
—

Weakness Classification(2)

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

Additional Vendor Advisories

(1)

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 / 34× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 88 of 179 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 12 repeat rows among the latest 100 are merged into the row they repeat. The 91 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-11 13:43 UTCEPSS rescoreEPSS 5.9% · 93rd percentile
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  6. 2026-10-07 21:45 UTCEG score recompute▼ 0.20
  7. 2026-10-07 21:45 UTCVendor advisory
  8. 2026-10-07 21:23 UTCNVD updateCVSS v3 → 6.3
  9. 2026-10-07 20:46 UTCEG score recompute
  10. 2026-10-07 20:46 UTCVendor advisory
  11. 2026-10-06 15:14 UTCEPSS rescoreEPSS 5.9% · 93rd percentile
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  15. 2026-09-30 15:40 UTCEG score recompute
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  22. 2026-09-25 19:45 UTCOSV refresh
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  1. 2026-09-21 20:28 UTCEPSS rescoreEPSS 5.9% · 92nd percentile
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  14. 2026-09-06 10:00 UTCOSV refresh
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  31. 2026-08-19 20:34 UTCOSV refresh
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  58. 2026-07-23 02:03 UTCEG score recompute
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  60. 2026-07-22 14:06 UTCEPSS rescoreEPSS 5.9% · 92nd percentile
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Frequently asked(5)

What is CVE-2021-39140?
CVE-2021-39140 is a medium-severity vulnerability; its CVE record was published on August 23, 2021. XStream is a simple library to serialize objects to XML and back again. In affected versions this vulnerability may allow a remote attacker to allocate 100% CPU time on the target system depending on CPU type or parallel execution of such a payload resulting in a denial of service only by…
When was the CVE record for CVE-2021-39140 published?
The CVE record for CVE-2021-39140 was published on August 23, 2021. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of October 7, 2026; the record at its source may have been updated since.
Is CVE-2021-39140 actively exploited?
CVE-2021-39140 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 5.9% probability of exploitation in the next 30 days (93rd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2021-39140?
CVE-2021-39140 has a CVSS v3 base score of 6.3 (NVD).
How do I remediate CVE-2021-39140?
A fix for CVE-2021-39140 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2021-39140 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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