Debian Matrix-Synapse vulnerabilities

CVE-2026-45078 [HIGH] CWE-400 Synapse CPU starvation (Denial of Service) Synapse CPU starvation (Denial of Service) ### Impact Local authenticated users can cause Synapse to starve other requests of CPU and lead to other requests failing, causing other users to be denied service. Homeservers that trust all their local users are not at risk. ### Patches Update to Synapse 1.152.1 or later. ### Workarounds If Synapse is deployed behind a reverse proxy, the reverse proxy could be configured t

CVE-2026-45076 [MEDIUM] CWE-20 Synapse pagination Denial of Service Synapse pagination Denial of Service ### Impact In federated rooms, malicious homeservers can craft room events in such a way that prevents Synapse from providing full history to paginating clients. Clients could therefore fail to display room history. ### Patches Update to Synapse 1.152.1 or later. ### Workarounds There are no known workarounds for this issue. ### Identifiers - ELEMENTSEC-2025-1636 ### For more inform

CVE-2025-30355 [HIGH] CVE-2025-30355: matrix-synapse - Synapse is an open source Matrix homeserver implementation. A malicious server c... Synapse is an open source Matrix homeserver implementation. A malicious server can craft events which, when received, prevent Synapse version up to 1.127.0 from federating with other servers. The vulnerability has been exploited in the wild and has been fixed in Synapse v1.127.1. No known workarounds are available. Scope: local forky: resolved (fixed in 1.121

CVE-2025-61672 [MEDIUM] CVE-2025-61672: matrix-synapse - Synapse is an open source Matrix homeserver implementation. Lack of validation f... Synapse is an open source Matrix homeserver implementation. Lack of validation for device keys in Synapse before 1.138.3 and in Synapse 1.139.0 allow an attacker registered on the victim homeserver to degrade federation functionality, unpredictably breaking outbound federation to other homeservers. The issue is patched in Synapse 1.138.3, 1.138.4, 1.139.1,

CVE-2024-52815 [HIGH] CVE-2024-52815: matrix-synapse - Synapse is an open-source Matrix homeserver. Synapse versions before 1.120.1 fai... Synapse is an open-source Matrix homeserver. Synapse versions before 1.120.1 fail to properly validate invites received over federation. This vulnerability allows a malicious server to send a specially crafted invite that disrupts the invited user's /sync functionality. Synapse 1.120.1 rejects such invalid invites received over federation and restores the abi

CVE-2024-53863 [HIGH] CVE-2024-53863: matrix-synapse - Synapse is an open-source Matrix homeserver. In Synapse versions before 1.120.1,... Synapse is an open-source Matrix homeserver. In Synapse versions before 1.120.1, enabling the dynamic_thumbnails option or processing a specially crafted request could trigger the decoding and thumbnail generation of uncommon image formats, potentially invoking external tools like Ghostscript for processing. This significantly expands the attack surface in a

CVE-2024-37302 [HIGH] CVE-2024-37302: matrix-synapse - Synapse is an open-source Matrix homeserver. Synapse versions before 1.106 are v... Synapse is an open-source Matrix homeserver. Synapse versions before 1.106 are vulnerable to a disk fill attack, where an unauthenticated adversary can induce Synapse to download and cache large amounts of remote media. The default rate limit strategy is insufficient to mitigate this. This can lead to a denial of service, ranging from further media uploads/do

CVE-2024-52805 [HIGH] CVE-2024-52805: matrix-synapse - Synapse is an open-source Matrix homeserver. In Synapse before 1.120.1, multipar... Synapse is an open-source Matrix homeserver. In Synapse before 1.120.1, multipart/form-data requests can in certain configurations transiently increase memory consumption beyond expected levels while processing the request, which can be used to amplify denial of service attacks. Synapse 1.120.1 resolves the issue by denying requests with unsupported multipart

CVE-2024-31208 [MEDIUM] CVE-2024-31208: matrix-synapse - Synapse is an open-source Matrix homeserver. A remote Matrix user with malicious... Synapse is an open-source Matrix homeserver. A remote Matrix user with malicious intent, sharing a room with Synapse instances before 1.105.1, can dispatch specially crafted events to exploit a weakness in the V2 state resolution algorithm. This can induce high CPU consumption and accumulate excessive data in the database of such instances, resulting in a d

CVE-2024-37303 [MEDIUM] CVE-2024-37303: matrix-synapse - Synapse is an open-source Matrix homeserver. Synapse before version 1.106 allows... Synapse is an open-source Matrix homeserver. Synapse before version 1.106 allows, by design, unauthenticated remote participants to trigger a download and caching of remote media from a remote homeserver to the local media repository. Such content then also becomes available for download from the local homeserver in an unauthenticated way. The implication i

CVE-2024-53867 [MEDIUM] CVE-2024-53867: matrix-synapse - Synapse is an open-source Matrix homeserver. The Sliding Sync feature on Synapse... Synapse is an open-source Matrix homeserver. The Sliding Sync feature on Synapse versions between 1.113.0rc1 and 1.120.0 can leak partial room state changes to users no longer in a room. Non-state events, like messages, are unaffected. This vulnerability is fixed in 1.120.1. Scope: local forky: resolved (fixed in 1.121.0-1) sid: resolved (fixed in 1.121.0-1

CVE-2023-43796 [MEDIUM] CVE-2023-43796: matrix-synapse - Synapse is an open-source Matrix homeserver Prior to versions 1.95.1 and 1.96.0r... 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_do

CVE-2023-32323 [MEDIUM] CVE-2023-32323: matrix-synapse - Synapse is an open-source Matrix homeserver written and maintained by the Matrix... Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. A malicious user on a Synapse homeserver X with permission to create certain state events can disable outbound federation from X to an arbitrary homeserver Y. Synapse instances with federation disabled are not affected. In versions of Synapse up to and including

CVE-2023-32682 [MEDIUM] CVE-2023-32682: matrix-synapse - Synapse is a Matrix protocol homeserver written in Python with the Twisted frame... Synapse is a Matrix protocol homeserver written in Python with the Twisted framework. In affected versions it may be possible for a deactivated user to login when using uncommon configurations. This only applies if any of the following are true: 1. JSON Web Tokens are enabled for login via the `jwt_config.enabled` configuration setting. 2. The local passwor

CVE-2023-45129 [MEDIUM] CVE-2023-45129: matrix-synapse - Synapse is an open-source Matrix homeserver written and maintained by the Matrix... Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. Prior to version 1.94.0, a malicious server ACL event can impact performance temporarily or permanently leading to a persistent denial of service. Homeservers running on a closed federation (which presumably do not need to use server ACLs) are not affected. Serv

CVE-2023-41335 [LOW] CVE-2023-41335: matrix-synapse - Synapse is an open-source Matrix homeserver written and maintained by the Matrix... Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. When users update their passwords, the new credentials may be briefly held in the server database. While this doesn't grant the server any added capabilities—it already learns the users' passwords as part of the authentication process—it does disrupt the expectatio

CVE-2023-32683 [LOW] CVE-2023-32683: matrix-synapse - Synapse is a Matrix protocol homeserver written in Python with the Twisted frame... Synapse is a Matrix protocol homeserver written in Python with the Twisted framework. A discovered oEmbed or image URL can bypass the `url_preview_url_blacklist` setting potentially allowing server side request forgery or bypassing network policies. Impact is limited to IP addresses allowed by the `url_preview_ip_range_blacklist` setting (by default this only

CVE-2023-42453 [LOW] CVE-2023-42453: matrix-synapse - Synapse is an open-source Matrix homeserver written and maintained by the Matrix... 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

CVE-2022-31052 [MEDIUM] CVE-2022-31052: matrix-synapse - Synapse is an open source home server implementation for the Matrix chat network... Synapse is an open source home server implementation for the Matrix chat network. In versions prior to 1.61.1 URL previews of some web pages can exhaust the available stack space for the Synapse process due to unbounded recursion. This is sometimes recoverable and leads to an error for the request causing the problem, but in other cases the Synapse process

CVE-2022-41952 [MEDIUM] CVE-2022-41952: matrix-synapse - Synapse before 1.52.0 with URL preview functionality enabled will attempt to gen... Synapse before 1.52.0 with URL preview functionality enabled will attempt to generate URL previews for media stream URLs without properly limiting connection time. Connections will only be terminated after `max_spider_size` (default: 10M) bytes have been downloaded, which can in some cases lead to long-lived connections towards the streaming media server (f