CVE-2023-43796

MEDIUMNVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.3 under NVD CVSS v3. EPSS exploit probability: 0.9%, top 44% 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
5.3
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 1%CVSS: 5.3Exploit: NoneExposed: 0

A fix is available — apply it.

Synapse is an open-source Matrix homeserver Prior to versions 1.95.1 and 1.96.0rc1, cached device information of remote users can be queried from Synapse. This can be used to enumerate the remote users known to a homeserver. System administrators are encouraged to upgrade to Synapse 1.95.1 or 1.96.0rc1 to receive a patch. As a workaround, the federation_domain_whitelist can be used to limit federation traffic with a homeserver.

CVSS v3
5.3
EG Score
5.3(medium)
EG Risk
29(Track)
EG Risk 29/100SSVC: 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
Severity53% × 45%
Exploitation1% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
55.8%
KEV
Not listed

Published

October 31, 2023

Last Modified

June 17, 2026

References (10)

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-synapse0.33.5 ... 1.95.0rc1 (354 versions)1.95.1—

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 12× in last 7d / 49× 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 109 total refreshes for this CVE.

  1. 2026-07-23 02:26 UTCEG score recompute
  2. 2026-07-22 23:13 UTCEG score recompute
  3. 2026-07-22 14:06 UTCEPSS rescore
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  15. 2026-07-15 05:19 UTCOSV refresh
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  1. 2026-07-08 15:13 UTCEPSS rescore
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  50. 2026-06-09 16:17 UTCOSV refresh
  51. 2026-06-08 14:16 UTCEPSS rescore
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Frequently asked(5)

What is CVE-2023-43796?
CVE-2023-43796 is a medium vulnerability published on October 31, 2023. Synapse is an open-source Matrix homeserver Prior to versions 1.95.1 and 1.96.0rc1, cached device information of remote users can be queried from Synapse. This can be used to enumerate the remote users known to a homeserver. System administrators are encouraged to upgrade to Synapse 1.95.1 or…
When was CVE-2023-43796 disclosed?
CVE-2023-43796 was first published in the National Vulnerability Database on October 31, 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-2023-43796 actively exploited?
CVE-2023-43796 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 55.8% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2023-43796?
CVE-2023-43796 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2023-43796?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2023-43796, 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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