CVE-2022-31152 | Synapse vulnerable to denial of service (DoS) due to incorrect application of event authorization rules

Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. The Matrix specification specifies a list of [event authorization rules](https://spec.matrix.org/v1.2/rooms/v9/#authorization-rules) which must be checked when determining if an event should be accepted into a room. In versions of Synapse up to and including version 1.61.0, some of these rules are not correctly applied. An attacker could craft events which would be accepted by Synapse but not a spec-conformant server, potentially causing divergence in the room state between servers. Administrators of homeservers with federation enabled are advised to upgrade to version 1.62.0 or higher. Federation can be disabled by setting [`federation_domain_whitelist`](https://matrix-org.github.io/synapse/latest/usage/configuration/config_documentation.html#federation_domain_whitelist) to an empty list (`[]`) as a workaround.

Published: 2022-09-02 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2022-31152 is rated Moderate Risk (45/100): 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-2022-31152

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 0.69% 0.90% +0.21%
2 2025-09-04 0.53% 0.69% +0.16%
3 2025-09-03 — 0.53% —

Full EPSS history (10 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2022-31152

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.4 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H 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:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
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:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.6 4.7 [email protected]
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H 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:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]

Weakness enumeration for CVE-2022-31152

GitHub Security Advisory for CVE-2022-31152

GHSA-jhjh-776m-4765 · Severity: high · Ecosystem: pip — Denial of service due to incorrect application of event authorization rules

OS Trackers for CVE-2022-31152

vendor priority summary link
alpine high CVE-2022-31152: 1 source package rows (synapse); 16 state rows across 2 repos (3.22-community, edge-community); fixed 0, open 16. https://security.alpinelinux.org/vuln/CVE-2022-31152
debian not yet assigned CVE-2022-31152 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-2022-31152
ubuntu medium CVE-2022-31152 medium priority: Ubuntu including 1 source packages (matrix-synapse), 11 status rows across 11 suites (bionic, focal, jammy, kinetic, lunar, mantic, noble, oracular, trusty, upstream, xenial): not-affected 5, needs-triage 3, ignored 2, released 1. https://ubuntu.com/security/CVE-2022-31152

Affected software / configurations for CVE-2022-31152

Vendor Product Version Raw CPE
matrix synapse < 1.62.0 cpe:2.3:a:matrix:synapse:*:*:*:*:*:*:*:*

References for CVE-2022-31152

URL Tags
https://github.com/matrix-org/synapse/pull/13087 Issue Tracking Patch Third Party Advisory
https://github.com/matrix-org/synapse/pull/13088 Issue Tracking Patch Third Party Advisory
https://github.com/matrix-org/synapse/releases/tag/v1.62.0 Release Notes Third Party Advisory
https://github.com/matrix-org/synapse/security/advisories/GHSA-jhjh-776m-4765 Issue Tracking Mitigation Third Party Advisory
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