CVE-2023-42453

MEDIUMNVD 4.33.1▼
EchelonGraph scoreMEDIUM confidence

This low-severity CVE scores 3.1 under NVD CVSS v3. EPSS exploit probability: 0.2%, top 55% 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
4.3
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 1%CVSS: 4.3Exploit: NoneExposed: 0

A fix is available — apply it.

Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. Users were able to forge read receipts for any event (if they knew the room ID and event ID). Note that the users were not able to view the events, but simply mark it as read. This could be confusing as clients will show the event as read by the user, even if they are not in the room. This issue has been patched in version 1.93.0. Users are advised to upgrade. There are no known workarounds for this issue.

CVSS v3
4.3
EG Score
3.1(medium)
EPSS
46.8%
KEV
Not listed

Published

September 27, 2023

Last Modified

June 17, 2026

References (12)

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntumatrix-synapse (1.53.0-1ubuntu0.1~esm2) @ jammy2026-05-24ubuntu

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

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
matrix-synapse1.34.0 ... 1.93.0rc1 (180 versions)1.93.0—

Weakness Classification(1)

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

All Vendor Advisories

(1)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 7× in last 7d / 47× 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 08:26 UTCEPSS rescore
  2. 2026-07-11 08:26 UTCEPSS rescore
  3. 2026-07-09 19:08 UTCEPSS rescore
  4. 2026-07-08 15:13 UTCEPSS rescore
  5. 2026-07-06 16:26 UTCEPSS rescore
  6. 2026-07-06 16:26 UTCEPSS rescore
  7. 2026-07-06 02:22 UTCEPSS rescore
  8. 2026-07-05 02:29 UTCEPSS rescore
  9. 2026-07-04 06:29 UTCEPSS rescore
  10. 2026-07-01 15:05 UTCEPSS rescore
  11. 2026-06-30 23:21 UTCEPSS rescore
  12. 2026-06-30 23:21 UTCEPSS rescore
  13. 2026-06-29 14:05 UTCEPSS rescore
  14. 2026-06-28 14:06 UTCEPSS rescore
  15. 2026-06-28 14:06 UTCEPSS rescore
  16. 2026-06-28 04:55 UTCEPSS rescore
  17. 2026-06-28 04:55 UTCEPSS rescore
  18. 2026-06-27 09:34 UTCOSV refresh
  19. 2026-06-27 03:07 UTCEPSS rescore
  20. 2026-06-27 03:07 UTCEPSS rescore
  21. 2026-06-25 13:48 UTCEPSS rescore
  22. 2026-06-25 13:48 UTCEPSS rescore
  23. 2026-06-24 14:04 UTCEPSS rescore
  24. 2026-06-24 14:04 UTCEPSS rescore
  25. 2026-06-24 06:22 UTCNVD updateCVSS v3 → 4.3 · severity → MEDIUM
Show 62 more
  1. 2026-06-23 21:31 UTCEPSS rescore
  2. 2026-06-23 21:31 UTCEPSS rescore
  3. 2026-06-22 14:24 UTCEPSS rescore
  4. 2026-06-22 14:24 UTCEPSS rescore
  5. 2026-06-21 14:55 UTCEPSS rescore
  6. 2026-06-21 14:55 UTCEPSS rescore
  7. 2026-06-21 01:58 UTCEPSS rescore
  8. 2026-06-21 01:58 UTCEPSS rescore
  9. 2026-06-19 19:24 UTCEPSS rescore
  10. 2026-06-19 19:24 UTCEPSS rescore
  11. 2026-06-18 17:51 UTCEPSS rescore
  12. 2026-06-17 17:51 UTCEPSS rescore
  13. 2026-06-17 17:51 UTCEPSS rescore
  14. 2026-06-16 17:51 UTCEPSS rescore
  15. 2026-06-16 17:51 UTCEPSS rescore
  16. 2026-06-15 17:47 UTCEPSS rescore
  17. 2026-06-15 17:47 UTCEPSS rescore
  18. 2026-06-14 23:16 UTCEPSS rescore
  19. 2026-06-13 22:59 UTCEPSS rescore
  20. 2026-06-13 22:59 UTCEPSS rescore
  21. 2026-06-12 23:10 UTCEPSS rescore
  22. 2026-06-12 23:10 UTCEPSS rescore
  23. 2026-06-11 13:59 UTCEPSS rescore
  24. 2026-06-11 13:59 UTCEPSS rescore
  25. 2026-06-10 22:17 UTCEPSS rescore
  26. 2026-06-10 13:21 UTCEPSS rescore
  27. 2026-06-10 13:21 UTCEPSS rescore
  28. 2026-06-09 19:47 UTCOSV refresh
  29. 2026-06-08 14:16 UTCEPSS rescore
  30. 2026-06-08 14:16 UTCEPSS rescore
  31. 2026-06-07 15:23 UTCEPSS rescore
  32. 2026-06-07 15:23 UTCEPSS rescore
  33. 2026-06-06 13:46 UTCEPSS rescore
  34. 2026-06-06 13:46 UTCEPSS rescore
  35. 2026-06-05 22:46 UTCEPSS rescore
  36. 2026-06-05 22:46 UTCEPSS rescore
  37. 2026-06-05 06:09 UTCEPSS rescore
  38. 2026-06-05 06:09 UTCEPSS rescore
  39. 2026-06-05 06:09 UTCEPSS rescore
  40. 2026-06-04 13:11 UTCEPSS rescore
  41. 2026-06-04 13:11 UTCEPSS rescore
  42. 2026-06-02 20:12 UTCEPSS rescore
  43. 2026-06-02 20:12 UTCEPSS rescore
  44. 2026-06-01 13:51 UTCEPSS rescore
  45. 2026-06-01 13:51 UTCEPSS rescore
  46. 2026-05-31 22:30 UTCEPSS rescore
  47. 2026-05-31 22:29 UTCEPSS rescore
  48. 2026-05-31 00:15 UTCEPSS rescore
  49. 2026-05-31 00:15 UTCEPSS rescore
  50. 2026-05-29 13:43 UTCEPSS rescore
  51. 2026-05-29 13:43 UTCEPSS rescore
  52. 2026-05-28 13:44 UTCEPSS rescore
  53. 2026-05-28 13:43 UTCEPSS rescore
  54. 2026-05-27 13:39 UTCEPSS rescore
  55. 2026-05-27 13:39 UTCEPSS rescore
  56. 2026-05-26 13:43 UTCEPSS rescore
  57. 2026-05-26 13:43 UTCEPSS rescore
  58. 2026-05-26 07:18 UTCEPSS rescore
  59. 2026-05-26 07:18 UTCEPSS rescore
  60. 2026-05-26 07:18 UTCEPSS rescore
  61. 2026-05-24 17:02 UTCEG score recompute
  62. 2026-05-24 17:02 UTCVendor advisory

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2023-42453?
CVE-2023-42453 is a medium vulnerability published on September 27, 2023. Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. Users were able to forge read receipts for any event (if they knew the room ID and event ID). Note that the users were not able to view the events, but simply mark it as read. This could be confusing as…
When was CVE-2023-42453 disclosed?
CVE-2023-42453 was first published in the National Vulnerability Database on September 27, 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-2023-42453 actively exploited?
CVE-2023-42453 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 46.8% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2023-42453?
CVE-2023-42453 has a CVSS v3 base score of 4.3 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 3.1.
How do I remediate CVE-2023-42453?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2023-42453, 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

See which npm, PyPI, Go, and Maven packages are affected by CVE-2023-42453

Explore →

Is Your Infrastructure Affected by CVE-2023-42453?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs