CVE-2020-26217

CRITICALNVD 8.89.0
EchelonGraph scoreHIGH confidence

“▲” beside the score: it is higher than NVD's CVSS score.

Score elevated to 9.0 because EPSS predicted 83% probability of exploitation within the next 30 days (99th percentile of EPSS-scored CVEs) when EchelonGraph scored this CVE. NVD baseline CVSS 8.8 retained for reference. Confidence: see factors.

Triggered by: EPSS exploit prediction (continuous uplift above 30%)
Sources: EPSS, NVD CVSS v3
Trending — 3 sources updated this weekElevated
9.0EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • High exploitation likelihood — EPSS 83%
  • Public exploit or proof-of-concept code is available
CISA-KEV: Not listedEPSS PROB: 83%CVSS: 8.8Exploit: Public PoCExposed services: Not assessed

A fix is available — apply it.

XStream before version 1.4.14 is vulnerable to Remote Code Execution.The vulnerability may allow a remote attacker to run arbitrary shell commands only by manipulating the processed input stream. Only users who rely on blocklists are affected. Anyone using XStream's Security Framework allowlist is not affected. The linked advisory provides code workarounds for users who cannot upgrade. The issue is fixed in version 1.4.14.

CVSS v3
8.8
EG Score
9.0CRITICALhigh confidence
EG Risk
88
EG Risk 88/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity88% × 45%
Impact severity (EG Severity): CVSS 8.8 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation83% × 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 total (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
83%
EPSS %ILE
99th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (9.0): severity, escalated by confirmed exploitation. This CVE's 9.0 is EPSS's lift toward 9.0 from its impact severity (EG Severity, CVSS 8.8 HIGH): a likelihood of exploitation, not impact.

EG Severity
8.8 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
EG Likelihood
83% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-22). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 3 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.

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 total (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

BOD 26-04 (CISA's remediation timeline, Table 1)3 days if the affected system is publicly exposed; 60 days if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

November 16, 2020

Last Modified

October 7, 2026

Advisory Details (9)

Auto-updated Sep 20, 2026
Patch available. Sources: github_commit, github.

Patch Availability(7)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntulibxstream-java (1.4.15-1ubuntu0.1) @ hirsute2026-10-21ubuntu
ubuntulibxstream-java (1.4.11.1-1ubuntu0.1) @ focal2026-10-21ubuntu
ubuntulibxstream-java (1.4.8-1ubuntu0.1+esm3) @ xenial2026-10-21ubuntu
redhatxstream2021-12-14redhat
redhatpatch2021-11-23redhat
redhatpatch2021-08-18redhat
redhatxstream-0:1.3.1-12.el7_92021-01-18redhat

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
  • every version up to 1.4.11.1-1+deb10u1: fixed in 1.4.11.1-1+deb10u1
—
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
libxstream-java—
  • every version up to 1.4.14-1: fixed in 1.4.14-1
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
libxstream-java—
  • every version up to 1.4.14-1: fixed in 1.4.14-1
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
libxstream-java—
  • every version up to 1.4.14-1: fixed in 1.4.14-1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
libxstream-java—
  • every version up to 1.4.14-1: fixed in 1.4.14-1
—
Debian:9(1)
PackageVulnerable rangeFix by version rangeDependents
libxstream-java1.4.9-2
  • every version up to 1.4.9-2+deb9u1: fixed in 1.4.9-2+deb9u1
—
Maven(1)
PackageVulnerable rangeFix by version rangeDependents
com.thoughtworks.xstream:xstream0.1 ... 1.4.9 (37 versions)
  • every version up to 1.4.14-java7: fixed in 1.4.14-java7
—

Weakness Classification(1)

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

Additional Vendor Advisories

(6)

Data Freshness Timeline

(refreshed 18× in last 7d / 40× 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 89 of 98 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. 11 repeat rows among the latest 100 are merged into the row they repeat. The 9 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-22 23:16 UTCEG score recompute
  2. 2026-10-22 23:16 UTCVendor advisory
  3. 2026-10-22 16:29 UTCEPSS rescoreEPSS 83% · 99th percentile
  4. 2026-10-22 00:21 UTCEG score recompute
  5. 2026-10-22 00:21 UTCVendor advisory
  6. 2026-10-21 16:28 UTCEPSS rescoreEPSS 85% · 99th percentile
  7. 2026-10-21 01:24 UTCEG score recompute
  8. 2026-10-21 01:24 UTCVendor advisory
  9. 2026-10-20 02:27 UTCEG score recompute
  10. 2026-10-20 02:27 UTCVendor advisory
  11. 2026-10-19 16:27 UTCEPSS rescoreEPSS 85% · 99th percentile
  12. 2026-10-19 01:51 UTCEG score recompute
  13. 2026-10-19 01:51 UTCVendor advisory
  14. 2026-10-18 09:26 UTCEG score recompute
  15. 2026-10-18 02:53 UTCEG score recompute
  16. 2026-10-18 02:53 UTCVendor advisory
  17. 2026-10-17 03:56 UTCEG score recompute
  18. 2026-10-17 03:56 UTCVendor advisory
  19. 2026-10-16 16:33 UTCEPSS rescoreEPSS 85% · 99th percentile
  20. 2026-10-16 04:57 UTCEG score recompute
  21. 2026-10-16 04:57 UTCVendor advisory
  22. 2026-10-15 03:24 UTCEG score recompute
  23. 2026-10-15 03:24 UTCVendor advisory
  24. 2026-10-14 16:28 UTCEPSS rescoreEPSS 85% · 99th percentile
  25. 2026-10-13 23:36 UTCEG score recompute
Show 64 more
  1. 2026-10-13 23:36 UTCVendor advisory
  2. 2026-10-13 16:28 UTCEPSS rescoreEPSS 85% · 99th percentile
  3. 2026-10-12 19:40 UTCVendor advisory
  4. 2026-10-12 19:39 UTCEG score recompute
  5. 2026-10-12 00:03 UTCEG score recompute
  6. 2026-10-07 23:44 UTCEPSS rescoreEPSS 85% · 99th percentile
  7. 2026-10-07 19:28 UTCEG score recompute
  8. 2026-10-07 19:28 UTCVendor advisory
  9. 2026-10-07 19:19 UTCNVD updateCVSS v3 → 8.8
  10. 2026-10-07 19:03 UTCEG score recompute
  11. 2026-10-07 19:03 UTCVendor advisory
  12. 2026-10-03 14:22 UTCEPSS rescoreEPSS 85% · 99th percentile
  13. 2026-09-30 20:10 UTCOSV refresh
  14. 2026-09-30 15:16 UTCEG score recompute
  15. 2026-09-24 14:00 UTCEPSS rescoreEPSS 85% · 99th percentile
  16. 2026-09-22 14:43 UTCEPSS rescoreEPSS 85% · 99th percentile
  17. 2026-09-21 20:28 UTCEPSS rescoreEPSS 85% · 99th percentile
  18. 2026-09-19 15:37 UTCEPSS rescoreEPSS 85% · 99th percentile
  19. 2026-09-18 19:23 UTCEPSS rescoreEPSS 85% · 99th percentile
  20. 2026-09-16 14:04 UTCEPSS rescoreEPSS 85% · 99th percentile
  21. 2026-09-15 03:06 UTCEPSS rescoreEPSS 85% · 99th percentile
  22. 2026-09-12 02:40 UTCOSV refresh
  23. 2026-09-06 13:44 UTCEPSS rescoreEPSS 85% · 99th percentile
  24. 2026-09-05 15:24 UTCEPSS rescoreEPSS 85% · 99th percentile
  25. 2026-09-04 13:57 UTCEPSS rescoreEPSS 85% · 99th percentile
  26. 2026-09-02 14:08 UTCEPSS rescoreEPSS 85% · 99th percentile
  27. 2026-08-30 19:14 UTCEPSS rescoreEPSS 85% · 99th percentile
  28. 2026-08-26 14:42 UTCEPSS rescoreEPSS 85% · 99th percentile
  29. 2026-08-24 07:58 UTCOSV refresh
  30. 2026-08-20 22:52 UTCEPSS rescoreEPSS 85% · 99th percentile
  31. 2026-08-16 02:11 UTCEPSS rescoreEPSS 85% · 99th percentile
  32. 2026-08-13 21:57 UTCEPSS rescoreEPSS 85% · 99th percentile
  33. 2026-08-08 16:33 UTCEPSS rescoreEPSS 85% · 99th percentile
  34. 2026-08-08 04:49 UTCOSV refresh
  35. 2026-08-07 16:23 UTCEPSS rescoreEPSS 85% · 99th percentile
  36. 2026-07-28 15:33 UTCEPSS rescoreEPSS 85% · 99th percentile
  37. 2026-07-26 14:51 UTCEPSS rescoreEPSS 85% · 99th percentile
  38. 2026-07-24 14:14 UTCEPSS rescoreEPSS 85% · 99th percentile
  39. 2026-07-23 14:15 UTCEPSS rescoreEPSS 85% · 99th percentile
  40. 2026-07-23 01:51 UTCEG score recompute
  41. 2026-07-22 21:28 UTCEG score recompute▲ 1.00
  42. 2026-07-22 21:28 UTCVendor advisory
  43. 2026-07-22 14:05 UTCEPSS rescoreEPSS 85% · 99th percentile
  44. 2026-07-20 17:04 UTCEPSS rescoreEPSS 85% · 99th percentile
  45. 2026-07-16 16:59 UTCEPSS rescoreEPSS 85% · 99th percentile
  46. 2026-07-15 16:55 UTCEPSS rescoreEPSS 85% · 99th percentile
  47. 2026-07-12 23:07 UTCOSV refresh
  48. 2026-07-12 05:44 UTCEPSS rescoreEPSS 85% · 99th percentile
  49. 2026-07-09 19:07 UTCEPSS rescoreEPSS 85% · 99th percentile
  50. 2026-07-07 13:43 UTCEPSS rescoreEPSS 85% · 99th percentile
  51. 2026-07-06 16:25 UTCEPSS rescoreEPSS 85% · 99th percentile
  52. 2026-07-04 06:29 UTCEPSS rescoreEPSS 85% · 99th percentile
  53. 2026-06-27 03:06 UTCEPSS rescoreEPSS 85% · 99th percentile
  54. 2026-06-24 14:03 UTCEPSS rescoreEPSS 85% · 99th percentile
  55. 2026-06-24 08:50 UTCOSV refresh
  56. 2026-06-23 21:31 UTCEPSS rescoreEPSS 85% · 99th percentile
  57. 2026-06-21 14:54 UTCEPSS rescoreEPSS 85% · 99th percentile
  58. 2026-06-16 17:50 UTCEPSS rescoreEPSS 85% · 99th percentile
  59. 2026-06-15 17:46 UTCEPSS rescoreEPSS 85% · 99th percentile
  60. 2026-06-14 23:15 UTCEPSS rescoreEPSS 93% · 99th percentile
  61. 2026-06-12 23:10 UTCEPSS rescoreEPSS 93% · 99th percentile
  62. 2026-06-08 14:15 UTCEPSS rescoreEPSS 93% · 99th percentile
  63. 2026-06-07 15:23 UTCEPSS rescoreEPSS 93% · 99th percentile
  64. 2026-06-07 12:29 UTCOSV refresh

Publicly available exploits

(4 references)

Public exploit code is referenced for this CVE (3 GitHub PoCs), as is 1 Nuclei detection template. A detection template checks whether a system is affected; it is not necessarily exploit code. Defenders should treat patch urgency accordingly.

  • GitHub PoCKairo-one/CVE-2020-26217-XStream
    Published Dec 1, 2025

    CVE-2020-26217 XStream反序列化的poc

    Open source ↗
  • Nucleihttp/cves/2020/CVE-2020-26217.yaml
    Published Mar 29, 2023

    XStream <1.4.14 - Remote Code Execution

    Open source ↗
  • GitHub PoCAl1ex/CVE-2020-26217
    Published Jan 22, 2021

    CVE-2020-26217 && XStream RCE

    Open source ↗
  • GitHub PoCnovysodope/CVE-2020-26217-XStream-RCE-POC
    Published Dec 8, 2020

    CVE-2020-26217 XStream RCE POC

    Open source ↗

Frequently asked(5)

What is CVE-2020-26217?
CVE-2020-26217 is a critical-severity vulnerability; its CVE record was published on November 16, 2020. XStream before version 1.4.14 is vulnerable to Remote Code Execution.The vulnerability may allow a remote attacker to run arbitrary shell commands only by manipulating the processed input stream. Only users who rely on blocklists are affected. Anyone using XStream's Security Framework allowlist is…
When was the CVE record for CVE-2020-26217 published?
The CVE record for CVE-2020-26217 was published on November 16, 2020. 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-2020-26217 actively exploited?
CVE-2020-26217 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 83% probability of exploitation in the next 30 days (99th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2020-26217?
CVE-2020-26217 has a CVSS v3 base score of 8.8 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.0 (CRITICAL).
How do I remediate CVE-2020-26217?
A fix for CVE-2020-26217 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2020-26217 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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