CVE-2020-26890

HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 3.0%, top 14% of all CVEs by exploit prediction. 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
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 3%CVSS: 7.5Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Matrix Synapse before 1.20.0 erroneously permits non-standard NaN, Infinity, and -Infinity JSON values in fields of m.room.member events, allowing remote attackers to execute a denial of service attack against the federation and common Matrix clients. If such a malformed event is accepted into the room's state, the impact is long-lasting and is not fixed by an upgrade to a newer version, requiring the event to be manually redacted instead. Since events are replicated to servers of other room members, the impact is not constrained to the server of the event sender.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
39(Track)
EG Risk 39/100SSVC: Track

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
Severity75% × 45%
Exploitation3% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
85.8%
KEV
Not listed

Published

November 24, 2020

Last Modified

November 21, 2024

References (6)

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
matrix-synapse0.33.5 ... 1.9.1 (124 versions)1.20.0—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 12× in last 7d / 43× 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. 2026-07-23 01:52 UTCEG score recompute
  2. 2026-07-22 22:38 UTCEG score recompute
  3. 2026-07-22 14:05 UTCEPSS rescore
  4. 2026-07-21 15:22 UTCEPSS rescore
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  6. 2026-07-20 17:04 UTCEPSS rescore
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  8. 2026-07-19 14:28 UTCEPSS rescore
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  12. 2026-07-16 16:59 UTCEPSS rescore
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  15. 2026-07-15 01:57 UTCEPSS rescore
  16. 2026-07-13 22:27 UTCEPSS rescore
  17. 2026-07-13 22:27 UTCEPSS rescore
  18. 2026-07-12 22:38 UTCOSV refresh
  19. 2026-07-12 05:44 UTCEPSS rescore
  20. 2026-07-11 08:25 UTCEPSS rescore
  21. 2026-07-11 08:25 UTCEPSS rescore
  22. 2026-07-09 19:07 UTCEPSS rescore
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  24. 2026-07-07 13:43 UTCEPSS rescore
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  1. 2026-07-06 16:25 UTCEPSS rescore
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  6. 2026-06-30 23:20 UTCEPSS rescore
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  8. 2026-06-29 14:04 UTCEPSS rescore
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  11. 2026-06-27 03:06 UTCEPSS rescore
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  14. 2026-06-24 14:03 UTCEPSS rescore
  15. 2026-06-24 14:03 UTCEPSS rescore
  16. 2026-06-24 08:29 UTCOSV refresh
  17. 2026-06-23 21:31 UTCEPSS rescore
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  19. 2026-06-22 14:23 UTCEPSS rescore
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  21. 2026-06-21 14:54 UTCEPSS rescore
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  23. 2026-06-21 01:57 UTCEPSS rescore
  24. 2026-06-19 19:24 UTCEPSS rescore
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  26. 2026-06-18 17:50 UTCEPSS rescore
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  30. 2026-06-15 17:46 UTCEPSS rescore
  31. 2026-06-14 23:15 UTCEPSS rescore
  32. 2026-06-13 22:58 UTCEPSS rescore
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  35. 2026-06-10 22:16 UTCEPSS rescore
  36. 2026-06-10 13:20 UTCEPSS rescore
  37. 2026-06-08 14:15 UTCEPSS rescore
  38. 2026-06-07 15:23 UTCEPSS rescore
  39. 2026-06-07 15:23 UTCEPSS rescore
  40. 2026-06-07 15:23 UTCEPSS rescore
  41. 2026-06-07 12:29 UTCOSV refresh
  42. 2026-06-06 13:46 UTCEPSS rescore
  43. 2026-06-06 13:45 UTCEPSS rescore
  44. 2026-06-05 22:45 UTCEPSS rescore
  45. 2026-06-05 22:45 UTCEPSS rescore
  46. 2026-06-05 06:08 UTCEPSS rescore
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  48. 2026-06-04 13:10 UTCEPSS rescore
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  50. 2026-06-02 20:11 UTCEPSS rescore
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  52. 2026-06-01 13:50 UTCEPSS rescore
  53. 2026-05-31 22:29 UTCEPSS rescore
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  55. 2026-05-31 00:15 UTCEPSS rescore
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  57. 2026-05-29 13:42 UTCEPSS rescore
  58. 2026-05-28 13:43 UTCEPSS rescore
  59. 2026-05-28 13:43 UTCEPSS rescore
  60. 2026-05-27 13:39 UTCEPSS rescore
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  62. 2026-05-26 13:42 UTCEPSS rescore
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  64. 2026-05-26 07:17 UTCEPSS rescore
  65. 2026-05-26 07:17 UTCEPSS rescore
  66. 2026-05-23 04:55 UTCEG score recompute

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2020-26890?
CVE-2020-26890 is a high vulnerability published on November 24, 2020. Matrix Synapse before 1.20.0 erroneously permits non-standard NaN, Infinity, and -Infinity JSON values in fields of m.room.member events, allowing remote attackers to execute a denial of service attack against the federation and common Matrix clients. If such a malformed event is accepted into the…
When was CVE-2020-26890 disclosed?
CVE-2020-26890 was first published in the National Vulnerability Database on November 24, 2020, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2020-26890 actively exploited?
CVE-2020-26890 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 85.8% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2020-26890?
CVE-2020-26890 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2020-26890?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2020-26890, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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