CVE-2020-26259

HIGHNVD 6.88.9▲
EchelonGraph scoreHIGH confidence

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

Triggered by: EPSS exploit prediction (continuous uplift above 30%)
Sources: epss, nvd
Trending — 3 sources updated this weekElevated
8.9EG
EchelonGraph verdictPatch this weekExploitation is likely or a public exploit exists.
  • High exploitation likelihood — EPSS 82%
CISA-KEV: Not listedEPSS PROB: 82%CVSS: 6.8Exploit: 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 1.4.15, 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
88
EG Risk 88/100CISA 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
Severity89% × 45%
Exploitation82% × 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
82%
EPSS %ILE
99th
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 partial (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

December 16, 2020

Last Modified

October 7, 2026

Advisory Details (9)

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

NetApp Product Security

https://security.netapp.com/advisory/ntap-20210409-0005/
generic

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

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

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

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

Pony Mail

https://lists.apache.org/thread.html/r97993e3d78e1f5389b7b172ba9f308440830ce5f051ee62714a0aa34%40%3Ccommits.struts.apache.org%3E
generic

XStream - CVE-2020-26259

https://x-stream.github.io/CVE-2020-26259.html
githubMentions 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

Vendor Advisories for CVE-2020-26259(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 (1.4.15-1ubuntu0.1) @ hirsute2026-10-07ubuntu
ubuntulibxstream-java (1.4.8-1ubuntu0.1+esm3) @ xenial2026-10-07ubuntu
ubuntulibxstream-java (1.4.11.1-1ubuntu0.1) @ focal2026-10-07ubuntu
redhatxstream2021-12-14redhat
redhatpatch2021-11-23redhat
redhatpatch2021-08-18redhat

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, 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 5× in last 7d / 18× 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. 2026-10-07 23:44 UTCEPSS rescore
  2. 2026-10-07 19:28 UTCVendor advisory
  3. 2026-10-07 18:47 UTCEG score recompute
  4. 2026-10-07 18:47 UTCVendor advisory
  5. 2026-10-05 17:39 UTCEPSS rescore
  6. 2026-09-30 15:16 UTCEG score recompute
  7. 2026-09-30 14:59 UTCEPSS rescore
  8. 2026-09-27 13:41 UTCEPSS rescore
  9. 2026-09-26 15:54 UTCEPSS rescore
  10. 2026-09-26 15:54 UTCEPSS rescore
  11. 2026-09-24 14:00 UTCEPSS rescore
  12. 2026-09-22 14:43 UTCEPSS rescore
  13. 2026-09-21 20:28 UTCEPSS rescore
  14. 2026-09-19 19:00 UTCOSV refresh
  15. 2026-09-18 19:23 UTCEPSS rescore
  16. 2026-09-17 19:22 UTCEPSS rescore
  17. 2026-09-16 14:04 UTCEPSS rescore
  18. 2026-09-12 14:57 UTCEPSS rescore
  19. 2026-09-06 13:44 UTCEPSS rescore
  20. 2026-09-05 15:24 UTCEPSS rescore
  21. 2026-09-04 13:57 UTCEPSS rescore
  22. 2026-09-02 14:08 UTCEPSS rescore
  23. 2026-08-31 22:05 UTCOSV refresh
  24. 2026-08-30 19:14 UTCEPSS rescore
  25. 2026-08-30 01:18 UTCEPSS rescore
Show 59 more
  1. 2026-08-26 14:42 UTCEPSS rescore
  2. 2026-08-20 22:52 UTCEPSS rescore
  3. 2026-08-19 17:00 UTCEPSS rescore
  4. 2026-08-16 02:11 UTCEPSS rescore
  5. 2026-08-14 23:54 UTCOSV refresh
  6. 2026-08-13 21:57 UTCEPSS rescore
  7. 2026-07-30 12:44 UTCOSV refresh
  8. 2026-07-26 14:51 UTCEPSS rescore
  9. 2026-07-25 14:15 UTCEPSS rescore
  10. 2026-07-24 14:14 UTCEPSS rescore
  11. 2026-07-23 01:51 UTCEG score recompute▲ 2.10
  12. 2026-07-22 22:37 UTCEG score recompute
  13. 2026-07-22 14:05 UTCEPSS rescore
  14. 2026-07-21 15:22 UTCEPSS rescore
  15. 2026-07-21 15:22 UTCEPSS rescore
  16. 2026-07-20 17:04 UTCEPSS rescore
  17. 2026-07-20 17:04 UTCEPSS rescore
  18. 2026-07-15 16:55 UTCEPSS rescore
  19. 2026-07-15 16:55 UTCEPSS rescore
  20. 2026-07-15 01:57 UTCEPSS rescore
  21. 2026-07-12 21:38 UTCOSV refresh
  22. 2026-07-11 08:25 UTCEPSS rescore
  23. 2026-07-11 08:25 UTCEPSS rescore
  24. 2026-07-09 19:07 UTCEPSS rescore
  25. 2026-06-28 04:54 UTCEPSS rescore
  26. 2026-06-28 04:54 UTCEPSS rescore
  27. 2026-06-27 03:06 UTCEPSS rescore
  28. 2026-06-27 03:06 UTCEPSS rescore
  29. 2026-06-25 13:48 UTCEPSS rescore
  30. 2026-06-24 07:29 UTCOSV refresh
  31. 2026-06-23 21:31 UTCEPSS rescore
  32. 2026-06-23 21:31 UTCEPSS rescore
  33. 2026-06-21 01:57 UTCEPSS rescore
  34. 2026-06-17 17:50 UTCEPSS rescore
  35. 2026-06-15 17:46 UTCEPSS rescore
  36. 2026-06-12 23:10 UTCEPSS rescore
  37. 2026-06-11 13:58 UTCEPSS rescore
  38. 2026-06-10 22:16 UTCEPSS rescore
  39. 2026-06-10 13:20 UTCEPSS rescore
  40. 2026-06-07 10:59 UTCOSV refresh
  41. 2026-06-06 13:46 UTCEPSS rescore
  42. 2026-06-06 13:45 UTCEPSS rescore
  43. 2026-06-05 22:45 UTCEPSS rescore
  44. 2026-06-05 22:45 UTCEPSS rescore
  45. 2026-06-05 06:08 UTCEPSS rescore
  46. 2026-06-05 06:08 UTCEPSS rescore
  47. 2026-06-04 13:10 UTCEPSS rescore
  48. 2026-06-04 13:10 UTCEPSS rescore
  49. 2026-06-01 13:50 UTCEPSS rescore
  50. 2026-06-01 13:50 UTCEPSS rescore
  51. 2026-05-31 22:29 UTCEPSS rescore
  52. 2026-05-31 22:29 UTCEPSS rescore
  53. 2026-05-29 13:42 UTCEPSS rescore
  54. 2026-05-28 13:43 UTCEPSS rescore
  55. 2026-05-28 13:43 UTCEPSS rescore
  56. 2026-05-26 07:17 UTCEPSS rescore
  57. 2026-05-26 07:17 UTCEPSS rescore
  58. 2026-05-23 04:07 UTCEG score recompute
  59. 2026-05-23 04:07 UTCVendor advisory

Publicly available exploits

(1 reference)

Working exploit code is in the public domain (1 GitHub PoC). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCjas502n/CVE-2020-26259
    First seen 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 ↗

Related CVEs(same product + same vendor + same CWE)

Frequently asked(5)

What is CVE-2020-26259?
CVE-2020-26259 is a high vulnerability 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 CVE-2020-26259 disclosed?
CVE-2020-26259 was first published on December 16, 2020, 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-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 + CISA KEV + 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.

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