CVE-2023-43796 | Synapse vulnerable to leak of remote user device information

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.

Published: 2023-10-31 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2023-43796 is rated Moderate Risk (41/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 0.90%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2023-43796

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.23% 0.90% +0.66%
2 2026-06-11 0.27% 0.23% -0.03%
3 2026-05-24 — 0.27% —

Full EPSS history (16 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2023-43796

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 1.4 [email protected]
5.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 1.4 [email protected]

Weakness enumeration for CVE-2023-43796

GitHub Security Advisory for CVE-2023-43796

GHSA-mp92-3jfm-3575 · Severity: medium · Ecosystem: pip — Synapse vulnerable to leak of remote user device information

OS Trackers for CVE-2023-43796

vendor priority summary link
alpine — CVE-2023-43796: 1 source package rows (synapse); 34 state rows across 6 repos (3.18-community, 3.19-community, 3.20-community, 3.21-community, 3.22-community, edge-community); fixed 6, open 28. https://security.alpinelinux.org/vuln/CVE-2023-43796
debian not yet assigned CVE-2023-43796 not yet assigned priority: Debian including 1 source packages (matrix-synapse), 2 status rows across 2 suites (forky, sid): resolved 2. https://security-tracker.debian.org/tracker/CVE-2023-43796
gentoo low CVE-2023-43796: 1 GLSA(s) (202401-12), 1 atom(s) (net-im/synapse); latest impact low. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2023-43796
ubuntu medium CVE-2023-43796 medium priority: Ubuntu including 1 source packages (matrix-synapse), 10 status rows across 10 suites (bionic, focal, jammy, lunar, mantic, noble, oracular, trusty, upstream, xenial): ignored 4, released 4, not-affected 2. https://ubuntu.com/security/CVE-2023-43796

Affected software / configurations for CVE-2023-43796

Vendor Product Version Raw CPE
matrix synapse < 1.95.1 cpe:2.3:a:matrix:synapse:*:*:*:*:*:*:*:*
fedoraproject fedora 38 cpe:2.3:o:fedoraproject:fedora:38:*:*:*:*:*:*:*
fedoraproject fedora 39 cpe:2.3:o:fedoraproject:fedora:39:*:*:*:*:*:*:*

References for CVE-2023-43796

cvelogic Threat Intelligence