CVE-2023-45129

MEDIUMNVD 4.94.9—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 4.9 under NVD CVSS v3. EPSS exploit probability: 1.2% (66th percentile of EPSS-scored CVEs). 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
4.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 1.2%CVSS: 4.9Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. Prior to version 1.94.0, a malicious server ACL event can impact performance temporarily or permanently leading to a persistent denial of service. Homeservers running on a closed federation (which presumably do not need to use server ACLs) are not affected. Server administrators are advised to upgrade to Synapse 1.94.0 or later. As a workaround, rooms with malicious server ACL events can be purged and blocked using the admin API.

CVSS v3
4.9
EG Score
4.9MEDIUMmedium confidence
EG Risk
27
EG Risk 27/100CISA 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
Severity49% × 45%
Exploitation1% × 40%
Automatability30% × 15%
CISA SSVC: Track at low or medium mission impact; Track or 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
1.2%
EPSS %ILE
66th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track or 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 (no KEV listing, exploit record or EPSS ≥ 50%) · Automatable unknown (not published for this CVE) · Technical impact partial (CVSS below 9.0). 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

October 10, 2023

Last Modified

June 17, 2026

References (14)

Affected Packages

(2 across 2 ecosystems)
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
matrix-synapse0.19.2+dfsg-3 ... 1.94.0-1~bpo12+1 (279 versions)
  • every version up to 1.94.0-1: fixed in 1.94.0-1
—
PyPI(1)
PackageVulnerable rangeFix by version rangeDependents
matrix-synapse0.33.5 ... 1.94.0rc1 (351 versions)
  • every version up to 1.94.0: fixed in 1.94.0
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 8× in last 7d / 33× 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.

Showing the most recent 100 of 197 total refreshes for this CVE.

  1. 2026-10-09 20:05 UTCEPSS rescore
  2. 2026-10-08 17:06 UTCEPSS rescore
  3. 2026-10-07 23:46 UTCEPSS rescore
  4. 2026-10-06 15:15 UTCEPSS rescore
  5. 2026-10-05 17:41 UTCEPSS rescore
  6. 2026-10-04 23:20 UTCEPSS rescore
  7. 2026-10-03 14:23 UTCEPSS rescore
  8. 2026-10-03 14:23 UTCEPSS rescore
  9. 2026-10-01 19:48 UTCEPSS rescore
  10. 2026-09-30 16:31 UTCEG score recompute
  11. 2026-09-30 15:01 UTCEPSS rescore
  12. 2026-09-29 15:17 UTCEPSS rescore
  13. 2026-09-28 13:49 UTCEPSS rescore
  14. 2026-09-28 13:49 UTCEPSS rescore
  15. 2026-09-27 13:42 UTCEPSS rescore
  16. 2026-09-27 13:42 UTCEPSS rescore
  17. 2026-09-26 15:56 UTCEPSS rescore
  18. 2026-09-26 00:22 UTCEPSS rescore
  19. 2026-09-24 14:01 UTCEPSS rescore
  20. 2026-09-24 14:01 UTCEPSS rescore
  21. 2026-09-23 13:46 UTCEPSS rescore
  22. 2026-09-22 20:31 UTCOSV refresh
  23. 2026-09-20 20:14 UTCEPSS rescore
  24. 2026-09-20 20:14 UTCEPSS rescore
  25. 2026-09-18 19:25 UTCEPSS rescore
Show 75 more
  1. 2026-09-17 19:25 UTCEPSS rescore
  2. 2026-09-16 14:06 UTCEPSS rescore
  3. 2026-09-16 14:06 UTCEPSS rescore
  4. 2026-09-16 05:11 UTCEPSS rescore
  5. 2026-09-13 16:44 UTCEPSS rescore
  6. 2026-09-12 14:58 UTCEPSS rescore
  7. 2026-09-11 14:50 UTCEPSS rescore
  8. 2026-09-11 09:34 UTCEPSS rescore
  9. 2026-09-08 21:58 UTCEPSS rescore
  10. 2026-09-07 15:59 UTCEPSS rescore
  11. 2026-09-06 13:45 UTCEPSS rescore
  12. 2026-09-06 13:45 UTCEPSS rescore
  13. 2026-09-05 15:26 UTCEPSS rescore
  14. 2026-09-04 13:58 UTCEPSS rescore
  15. 2026-09-04 05:04 UTCEPSS rescore
  16. 2026-09-03 16:29 UTCOSV refresh
  17. 2026-09-02 14:09 UTCEPSS rescore
  18. 2026-09-01 13:51 UTCEPSS rescore
  19. 2026-08-30 19:15 UTCEPSS rescore
  20. 2026-08-30 01:20 UTCEPSS rescore
  21. 2026-08-28 21:39 UTCEPSS rescore
  22. 2026-08-27 14:23 UTCEPSS rescore
  23. 2026-08-26 14:44 UTCEPSS rescore
  24. 2026-08-26 14:43 UTCEPSS rescore
  25. 2026-08-25 13:46 UTCEPSS rescore
  26. 2026-08-23 00:17 UTCEPSS rescore
  27. 2026-08-21 23:47 UTCEPSS rescore
  28. 2026-08-20 22:53 UTCEPSS rescore
  29. 2026-08-19 17:02 UTCEPSS rescore
  30. 2026-08-19 17:02 UTCEPSS rescore
  31. 2026-08-18 13:46 UTCEPSS rescore
  32. 2026-08-17 13:45 UTCEPSS rescore
  33. 2026-08-17 05:50 UTCOSV refresh
  34. 2026-08-16 14:54 UTCEPSS rescore
  35. 2026-08-16 02:12 UTCEPSS rescore
  36. 2026-08-15 01:28 UTCEPSS rescore
  37. 2026-08-15 01:28 UTCEPSS rescore
  38. 2026-08-13 21:58 UTCEPSS rescore
  39. 2026-08-12 13:48 UTCEPSS rescore
  40. 2026-08-11 13:39 UTCEPSS rescore
  41. 2026-08-09 13:44 UTCEPSS rescore
  42. 2026-08-09 13:44 UTCEPSS rescore
  43. 2026-08-08 16:35 UTCEPSS rescore
  44. 2026-08-07 16:25 UTCEPSS rescore
  45. 2026-08-06 13:45 UTCEPSS rescore
  46. 2026-08-05 19:15 UTCEPSS rescore
  47. 2026-08-04 15:07 UTCEPSS rescore
  48. 2026-08-03 10:34 UTCEPSS rescore
  49. 2026-08-03 10:34 UTCEPSS rescore
  50. 2026-08-02 02:25 UTCEPSS rescore
  51. 2026-08-02 02:25 UTCEPSS rescore
  52. 2026-08-02 00:36 UTCOSV refresh
  53. 2026-08-01 04:14 UTCEPSS rescore
  54. 2026-08-01 04:13 UTCEPSS rescore
  55. 2026-07-30 16:26 UTCEPSS rescore
  56. 2026-07-30 16:26 UTCEPSS rescore
  57. 2026-07-30 01:28 UTCEPSS rescore
  58. 2026-07-30 01:28 UTCEPSS rescore
  59. 2026-07-28 15:34 UTCEPSS rescore
  60. 2026-07-28 15:34 UTCEPSS rescore
  61. 2026-07-25 14:16 UTCEPSS rescore
  62. 2026-07-24 14:16 UTCEPSS rescore
  63. 2026-07-23 14:16 UTCEPSS rescore
  64. 2026-07-23 14:16 UTCEPSS rescore
  65. 2026-07-23 02:27 UTCEG score recompute
  66. 2026-07-22 23:13 UTCEG score recompute
  67. 2026-07-22 14:06 UTCEPSS rescore
  68. 2026-07-21 15:23 UTCEPSS rescore
  69. 2026-07-21 15:23 UTCEPSS rescore
  70. 2026-07-20 17:06 UTCEPSS rescore
  71. 2026-07-19 14:29 UTCEPSS rescore
  72. 2026-07-19 02:27 UTCEPSS rescore
  73. 2026-07-18 10:03 UTCEPSS rescore
  74. 2026-07-18 10:03 UTCEPSS rescore
  75. 2026-07-16 17:01 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2023-45129?
CVE-2023-45129 is a medium vulnerability published on October 10, 2023. Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. Prior to version 1.94.0, a malicious server ACL event can impact performance temporarily or permanently leading to a persistent denial of service. Homeservers running on a closed federation (which…
When was CVE-2023-45129 disclosed?
CVE-2023-45129 was first published on October 10, 2023, with the most recent update on June 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2023-45129 actively exploited?
CVE-2023-45129 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1.2% probability of exploitation in the next 30 days (66th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2023-45129?
CVE-2023-45129 has a CVSS v3 base score of 4.9 (NVD).
How do I remediate CVE-2023-45129?
A fix for CVE-2023-45129 is available: update to the fixed version the vendor names in its advisory.

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