CVE-2021-39164

LOWNVD 3.13.1—
EchelonGraph scoreMEDIUM confidence

This low-severity CVE scores 3.1 under NVD CVSS v3. EPSS exploit probability: 0.5%, top 34% 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
3.1
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 1%CVSS: 3.1Exploit: NoneExposed: 0

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

Matrix is an ecosystem for open federated Instant Messaging and Voice over IP. In versions 1.41.0 and prior, unauthorised users can access the membership (list of members, with their display names) of a room if they know the ID of the room. The vulnerability is limited to rooms with shared history visibility. Furthermore, the unauthorised user must be using an account on a vulnerable homeserver that is in the room. Server administrators should upgrade to 1.41.1 or later in order to receive the patch. One workaround is available. Administrators of servers that use a reverse proxy could, with potentially unacceptable loss of functionality, block the endpoints: /_matrix/client/r0/rooms/{room_id}/members with at query parameter, and /_matrix/client/unstable/rooms/{room_id}/members with at query parameter.

CVSS v3
3.1
EG Score
3.1(medium)
EPSS
70.4%
KEV
Not listed

Published

August 31, 2021

Last Modified

November 21, 2024

References (10)

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
matrix-synapse0.33.5 ... 1.9.1 (197 versions)1.41.1—

Weakness Classification(2)

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

Data Freshness Timeline

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

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2021-39164?
CVE-2021-39164 is a low vulnerability published on August 31, 2021. Matrix is an ecosystem for open federated Instant Messaging and Voice over IP. In versions 1.41.0 and prior, unauthorised users can access the membership (list of members, with their display names) of a room if they know the ID of the room. The vulnerability is limited to rooms with shared history…
When was CVE-2021-39164 disclosed?
CVE-2021-39164 was first published in the National Vulnerability Database on August 31, 2021, 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-2021-39164 actively exploited?
CVE-2021-39164 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 70.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-39164?
CVE-2021-39164 has a CVSS v3 base score of 3.1 (NVD).
How do I remediate CVE-2021-39164?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-39164, 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.

Dependency Blast Radius

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