Information Disclosure in matrix-synapse (CVE-2021-39164)
Summary
Vulnerability in matrix-synapse (CVE-2021-39164). Risk of unauthorized operations or information disclosure. Exploitable via shared. Mitigation: upgrade to 1.41.1 or later.
Original description
The description as published by the source.
Impact
Unauthorised users can access the membership (list of members, with their display names) of a room if they know the ID of the room. The vulnerability is limited to rooms with shared history visibility. Furthermore, the unauthorised user must be using an account on a vulnerable homeserver that is in the room.
Patches
Server administrators should upgrade to 1.41.1 or later.
Workarounds
Administrators of servers that use a reverse proxy could, with potentially unacceptable loss of functionality, block the following endpoints:
/_matrix/client/r0/rooms/{room_id}/memberswithatquery parameter/_matrix/client/unstable/rooms/{room_id}/memberswithatquery parameter
References
n/a
For more information
If you have any questions or comments about this advisory, e-mail us at security@matrix.org.
Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2021-39164 has been found in matrix-synapse.
Attackers can target a specific entry point like shared over the network to misuse the product.
Risk of unauthorized operations or information disclosure.
What to do: upgrade matrix-synapse to 1.41.1 or later.
If unsure, ask your IT team or search "matrix-synapse CVE-2021-39164" on the vendor's site.
CVE-2021-39164 (matrix-synapse) — CWE-200
Attack vector: remote (network-reachable) / no user interaction
Attack surface: shared
Patched: 1.41.1 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Information disclosure (CWE-200) exists in matrix-synapse. Attackers reach the vulnerable code path via shared.
Check the vendor advisory for the affected versions of matrix-synapse. Attack surface: shared.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 1.41.1.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'matrix-synapse' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'matrix-synapse' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
matrix-synapseを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade matrix-synapse to 1.41.1ステージング環境で 1.41.1 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2021-39164 matrix-synapse Fixed in: 1.41.1-1
References
- advisory nvd.nist.gov
- package github.com
- web github.com
- web github.com
- web github.com
- web github.com
- web lists.fedoraproject.org
- web lists.fedoraproject.org