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matrix-synapse vulnerabilities

Vulnerabilities published for matrix-synapse in the last 30 days: 0. Listed in the KEV catalogue: 0.

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Vulnerabilities: 10

  1. CVE-2026-45078

    Medium · CVSS 6.8EPSS 0.13%No fix published

    Synapse CPU starvation (Denial of Service)

    Synapse is an open source Matrix homeserver implementation. Prior to 1.152.1, 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. This vulnerability is fixed in 1.152.1.

    Published Updated
  2. CVE-2026-45076

    Medium · CVSS 5.1EPSS 0.37%No fix published

    Synapse pagination denial of service

    Synapse is an open source Matrix homeserver implementation. Prior to 1.152.1, 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. This vulnerability is fixed in 1.152.1.

    Published Updated
  3. CVE-2025-61672

    Medium · CVSS 5.3EPSS 0.48%No fix published

    Synapse: Invalid device keys degrade federation functionality

    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, and 1.139.2. Note that even though 1.138.3 and 1.139.1 fix the vulnerability, they inadvertently introduced an unrelated regression. For this reason, the maintainers of Synapse recommend skipping these releases and upgrading straight to 1.138.4 and 1.139.2.

    Published Updated
  4. CVE-2025-30355

    High · CVSS 7.1EPSS 1.23%No fix published

    Synapse vulnerable to federation denial of service via malformed events

    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.

    Published Updated
  5. CVE-2024-37303

    Medium · CVSS 5.3EPSS 0.43%No fix published

    Synapse unauthenticated writes to the media repository allow planting of problematic content

    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 is that unauthenticated remote adversaries can use this functionality to plant problematic content into the media repository. Synapse 1.106 introduces a partial mitigation in the form of new endpoints which require authentication for media downloads. The unauthenticated endpoints will be fro

    Published Updated
  6. CVE-2024-37302

    High · CVSS 7.5EPSS 0.6%No fix published

    Synapse denial of service through media disk space consumption

    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/downloads failing to completely unavailability of the Synapse process, depending on how Synapse was deployed. Synapse 1.106 introduces a new "leaky bucket" rate limit on remote media downloads to reduce the amount of data a user can request at a time. This does not fully address the issue,

    Published Updated
  7. CVE-2024-52805

    High · CVSS 8.2EPSS 0.74%No fix published

    Synapse allows unsupported content types to lead to memory exhaustion

    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/form-data content type.

    Published Updated
  8. CVE-2024-52815

    High · CVSS 8.7EPSS 0.57%No fix published

    Synapse allows a a malformed invite to break the invitee's `/sync`

    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 ability to sync for affected users.

    Published Updated
  9. CVE-2024-53863

    High · CVSS 8.2EPSS 0.61%No fix published

    Synapse can be forced to thumbnail unexpected file formats, invoking external, potentially untrustworthy decoders

    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 historically vulnerable area, presenting a risk that far outweighs the benefit, particularly since these formats are rarely used on the open web or within the Matrix ecosystem. Synapse 1.120.1 addresses the issue by restricting thumbnail generation to images in the following widely used f

    Published Updated
  10. CVE-2024-31208

    Medium · CVSS 6.5EPSS 1.46%No fix published

    Synapse's V2 state resolution weakness allows DoS from remote room members

    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 denial of service. Servers in private federations, or those that do not federate, are not affected. Server administrators should upgrade to 1.105.1 or later. Some workarounds are available. One can ban the malicious users or ACL block servers from the rooms and/or leave the room and purge th

    Published Updated

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