CVE-2020-26259

HIGHNVD 6.88.9
EchelonGraph scoreHIGH confidence

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

Score elevated to 8.9 because EPSS predicted 82% probability of exploitation within the next 30 days (99th percentile of EPSS-scored CVEs) when EchelonGraph scored this CVE. NVD baseline CVSS 6.8 retained for reference. Confidence: see factors.

Triggered by: EPSS exploit prediction (continuous uplift above 30%)
Sources: EPSS, GitHub Security Advisory, NVD CVSS v3
Trending — 4 sources updated this weekElevated

Also known asEUVD-2020-1497 (ENISA EUVD) · GHSA-jfvx-7wrx-43fh (GitHub Security Advisories)Source: ENISA EUVD

8.9EG
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 82%
  • Public exploit or proof-of-concept code is available
CISA-KEV: Not listedEPSS PROB: 82%CVSS: 6.8Exploit: Public PoCExposed 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 1.4.15, is vulnerable to an Arbitrary File Deletion on the local host when unmarshalling. The vulnerability may allow a remote attacker to delete arbitrary know files on the host as log as the executing process has sufficient rights only by manipulating the processed input stream. If you rely on XStream's default blacklist of the Security Framework, you will have to use at least version 1.4.15. The reported vulnerability does not exist running Java 15 or higher. No user is affected, who followed the recommendation to setup XStream's Security Framework with a whitelist! Anyone relying on XStream's default blacklist can immediately switch to a whilelist for the allowed types to avoid the vulnerability. Users of XStream 1.4.14 or below who still want to use XStream default blacklist can use a workaround described in more detailed in the referenced advisories.

CVSS v3
6.8
EG Score
8.9HIGHhigh confidence
EG Risk
79
EG Risk 79/100

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)
Severity68% × 45%
Impact severity (EG Severity): CVSS 6.8 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation82% × 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
82%
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 (8.9): severity, escalated by confirmed exploitation. This CVE's 8.9 is EPSS's lift toward 9.0 from its impact severity (EG Severity, CVSS 6.8 MEDIUM): a likelihood of exploitation, not impact.

EG Severity
6.8 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
82% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-31). 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: 14 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source, and whom BOD 26-04 binds: 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 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

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; 60 days if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (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

December 16, 2020

Last Modified

October 7, 2026

Advisory Details (9)

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

[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/
Web page

[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/
Web page

[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/
Web page

[SECURITY] [DSA 4828-1] libxstream-java security update

https://www.debian.org/security/2021/dsa-4828
Web pageMentions a patch (unverified)

[SECURITY] [DLA 2507-1] libxstream-java security update

https://lists.debian.org/debian-lts-announce/2020/12/msg00042.html
Web page

XStream - CVE-2020-26259

https://x-stream.github.io/CVE-2020-26259.html
GitHub advisoryMentions a patch (unverified)

XStream is vulnerable to an Arbitrary File Deletion on the local host when unmarshalling · Advisory · x-stream/xstream · GitHub

https://github.com/x-stream/xstream/security/advisories/GHSA-jfvx-7wrx-43fh

Patch Availability(7)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntulibxstream-java (1.4.11.1-1~18.04.2) @ bionic2026-10-28ubuntu
ubuntulibxstream-java (1.4.8-1ubuntu0.1+esm3) @ xenial2026-10-28ubuntu
ubuntulibxstream-java (1.4.11.1-1ubuntu0.1) @ focal2026-10-28ubuntu
redhatxstream2021-12-14redhat
redhatpatch2021-11-23redhat
redhatpatch2021-08-18redhat
mavencom.thoughtworks.xstream:xstream @ 1.4.15 (fixes < 1.4.15)—ghsa

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
  • every version up to 1.4.11.1-1+deb10u2: fixed in 1.4.11.1-1+deb10u2
—
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
libxstream-java—
  • every version up to 1.4.15-1: fixed in 1.4.15-1
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
libxstream-java—
  • every version up to 1.4.15-1: fixed in 1.4.15-1
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
libxstream-java—
  • every version up to 1.4.15-1: fixed in 1.4.15-1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
libxstream-java—
  • every version up to 1.4.15-1: fixed in 1.4.15-1
—
Debian:9(1)
PackageVulnerable rangeFix by version rangeDependents
libxstream-java1.4.10-1, 1.4.11-1, 1.4.11.1-1, 1.4.9-2, 1.4.9-2+deb9u1
  • every version up to 1.4.11.1-1+deb9u1: fixed in 1.4.11.1-1+deb9u1
—
Maven(1)
PackageVulnerable rangeFix by version rangeDependents
com.thoughtworks.xstream:xstream0.1 ... 1.4.9 (39 versions)
  • every version up to 1.4.15: fixed in 1.4.15
—

Weakness Classification(1)

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 7× in last 7d / 25× 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 85 of 89 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. 15 repeat rows among the latest 100 are merged into the row they repeat. The 4 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-01 08:36 UTCGHSA enrichmentGHSA-jfvx-7wrx-43fh · GitHub severity MODERATE · GitHub CVSS 6.8
  2. 2026-11-01 08:36 UTCEG score recompute
  3. 2026-10-31 16:28 UTCEPSS rescoreEPSS 82% · 99th percentile
  4. 2026-10-30 16:29 UTCEPSS rescoreEPSS 82% · 99th percentile
  5. 2026-10-28 15:32 UTCEG score recompute
  6. 2026-10-28 15:32 UTCVendor advisory
  7. 2026-10-27 16:28 UTCEPSS rescoreEPSS 82% · 99th percentile
  8. 2026-10-25 18:46 UTCEG score recompute
  9. 2026-10-25 16:28 UTCEPSS rescoreEPSS 82% · 99th percentile
  10. 2026-10-22 16:29 UTCEPSS rescoreEPSS 82% · 99th percentile
  11. 2026-10-21 16:28 UTCEPSS rescoreEPSS 82% · 99th percentile
  12. 2026-10-21 12:20 UTCEG score recompute
  13. 2026-10-21 12:20 UTCVendor advisory
  14. 2026-10-20 16:28 UTCEPSS rescoreEPSS 82% · 99th percentile
  15. 2026-10-18 09:26 UTCEG score recompute
  16. 2026-10-15 16:27 UTCEPSS rescoreEPSS 82% · 99th percentile
  17. 2026-10-14 16:28 UTCEPSS rescoreEPSS 82% · 99th percentile
  18. 2026-10-12 19:39 UTCEG score recompute
  19. 2026-10-12 00:02 UTCEG score recompute
  20. 2026-10-10 19:56 UTCEPSS rescoreEPSS 82% · 99th percentile
  21. 2026-10-07 23:44 UTCEPSS rescoreEPSS 82% · 99th percentile
  22. 2026-10-07 19:28 UTCVendor advisory
  23. 2026-10-07 18:47 UTCEG score recompute
  24. 2026-10-07 18:47 UTCVendor advisory
  25. 2026-10-05 17:39 UTCEPSS rescoreEPSS 82% · 99th percentile
Show 60 more
  1. 2026-09-30 15:16 UTCEG score recompute
  2. 2026-09-30 14:59 UTCEPSS rescoreEPSS 82% · 99th percentile
  3. 2026-09-27 13:41 UTCEPSS rescoreEPSS 82% · 99th percentile
  4. 2026-09-26 15:54 UTCEPSS rescoreEPSS 82% · 99th percentile
  5. 2026-09-24 14:00 UTCEPSS rescoreEPSS 82% · 99th percentile
  6. 2026-09-22 14:43 UTCEPSS rescoreEPSS 82% · 99th percentile
  7. 2026-09-21 20:28 UTCEPSS rescoreEPSS 82% · 99th percentile
  8. 2026-09-19 19:00 UTCOSV refresh
  9. 2026-09-18 19:23 UTCEPSS rescoreEPSS 82% · 99th percentile
  10. 2026-09-17 19:22 UTCEPSS rescoreEPSS 82% · 99th percentile
  11. 2026-09-16 14:04 UTCEPSS rescoreEPSS 82% · 99th percentile
  12. 2026-09-12 14:57 UTCEPSS rescoreEPSS 82% · 99th percentile
  13. 2026-09-06 13:44 UTCEPSS rescoreEPSS 82% · 99th percentile
  14. 2026-09-05 15:24 UTCEPSS rescoreEPSS 82% · 99th percentile
  15. 2026-09-04 13:57 UTCEPSS rescoreEPSS 82% · 99th percentile
  16. 2026-09-02 14:08 UTCEPSS rescoreEPSS 82% · 99th percentile
  17. 2026-08-31 22:05 UTCOSV refresh
  18. 2026-08-30 19:14 UTCEPSS rescoreEPSS 82% · 99th percentile
  19. 2026-08-30 01:18 UTCEPSS rescoreEPSS 82% · 99th percentile
  20. 2026-08-26 14:42 UTCEPSS rescoreEPSS 82% · 99th percentile
  21. 2026-08-20 22:52 UTCEPSS rescoreEPSS 82% · 99th percentile
  22. 2026-08-19 17:00 UTCEPSS rescoreEPSS 82% · 99th percentile
  23. 2026-08-16 02:11 UTCEPSS rescoreEPSS 82% · 99th percentile
  24. 2026-08-14 23:54 UTCOSV refresh
  25. 2026-08-13 21:57 UTCEPSS rescoreEPSS 82% · 99th percentile
  26. 2026-07-30 12:44 UTCOSV refresh
  27. 2026-07-26 14:51 UTCEPSS rescoreEPSS 82% · 99th percentile
  28. 2026-07-25 14:15 UTCEPSS rescoreEPSS 82% · 99th percentile
  29. 2026-07-24 14:14 UTCEPSS rescoreEPSS 82% · 99th percentile
  30. 2026-07-23 01:51 UTCEG score recompute▲ 2.10
  31. 2026-07-22 22:37 UTCEG score recompute
  32. 2026-07-22 14:05 UTCEPSS rescoreEPSS 82% · 99th percentile
  33. 2026-07-21 15:22 UTCEPSS rescoreEPSS 82% · 99th percentile
  34. 2026-07-20 17:04 UTCEPSS rescoreEPSS 82% · 99th percentile
  35. 2026-07-15 16:55 UTCEPSS rescoreEPSS 82% · 99th percentile
  36. 2026-07-15 01:57 UTCEPSS rescoreEPSS 82% · 99th percentile
  37. 2026-07-12 21:38 UTCOSV refresh
  38. 2026-07-11 08:25 UTCEPSS rescoreEPSS 82% · 99th percentile
  39. 2026-07-09 19:07 UTCEPSS rescoreEPSS 82% · 99th percentile
  40. 2026-06-28 04:54 UTCEPSS rescoreEPSS 83% · 99th percentile
  41. 2026-06-27 03:06 UTCEPSS rescoreEPSS 81% · 99th percentile
  42. 2026-06-25 13:48 UTCEPSS rescoreEPSS 81% · 99th percentile
  43. 2026-06-24 07:29 UTCOSV refresh
  44. 2026-06-23 21:31 UTCEPSS rescoreEPSS 81% · 99th percentile
  45. 2026-06-21 01:57 UTCEPSS rescoreEPSS 81% · 99th percentile
  46. 2026-06-17 17:50 UTCEPSS rescoreEPSS 81% · 99th percentile
  47. 2026-06-15 17:46 UTCEPSS rescoreEPSS 81% · 99th percentile
  48. 2026-06-12 23:10 UTCEPSS rescoreEPSS 89% · 99th percentile
  49. 2026-06-11 13:58 UTCEPSS rescoreEPSS 89% · 99th percentile
  50. 2026-06-10 22:16 UTCEPSS rescoreEPSS 89% · 99th percentile
  51. 2026-06-10 13:20 UTCEPSS rescoreEPSS 89% · 99th percentile
  52. 2026-06-07 10:59 UTCOSV refresh
  53. 2026-06-06 13:45 UTCEPSS rescoreEPSS 89% · 99th percentile
  54. 2026-06-05 22:45 UTCEPSS rescoreEPSS 89% · 99th percentile
  55. 2026-06-05 06:08 UTCEPSS rescoreEPSS 89% · 99th percentile
  56. 2026-06-04 13:10 UTCEPSS rescoreEPSS 89% · 99th percentile
  57. 2026-06-01 13:50 UTCEPSS rescoreEPSS 89% · 99th percentile
  58. 2026-05-31 22:29 UTCEPSS rescoreEPSS 89% · 99th percentile
  59. 2026-05-29 13:42 UTCEPSS rescoreEPSS 89% · 99th percentile
  60. 2026-05-28 13:43 UTCEPSS rescoreEPSS 89% · 99th percentile

Publicly available exploits

(1 reference)

Public exploit code is referenced for this CVE (1 GitHub PoC). Defenders should treat patch urgency accordingly.

  • GitHub PoCjas502n/CVE-2020-26259
    Published Dec 13, 2020

    CVE-2020-26259: XStream is vulnerable to an Arbitrary File Deletion on the local host when unmarshalling as long as the executing process has sufficient rights.

    Open source ↗

Frequently asked(5)

What is CVE-2020-26259?
CVE-2020-26259 is a high-severity vulnerability; its CVE record was published on December 16, 2020. XStream is a Java library to serialize objects to XML and back again. In XStream before version 1.4.15, is vulnerable to an Arbitrary File Deletion on the local host when unmarshalling. The vulnerability may allow a remote attacker to delete arbitrary know files on the host as log as the executing…
When was the CVE record for CVE-2020-26259 published?
The CVE record for CVE-2020-26259 was published on December 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-2020-26259 actively exploited?
CVE-2020-26259 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 82% probability of exploitation in the next 30 days (99th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2020-26259?
CVE-2020-26259 has a CVSS v3 base score of 6.8 (NVD). EchelonGraph synthesises NVD + FIRST EPSS + GHSA into a combined EG score of 8.9 (HIGH).
How do I remediate CVE-2020-26259?
A fix for CVE-2020-26259 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2020-26259 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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