id: PYSEC-2021-27
details: Synapse is a Matrix reference homeserver written in python (pypi package
  matrix-synapse). Matrix is an ecosystem for open federated Instant Messaging and
  VoIP. In Synapse before version 1.28.0 Synapse is missing input validation of some
  parameters on the endpoints used to confirm third-party identifiers could cause
  excessive use of disk space and memory leading to resource exhaustion. Note that
  the groups feature is not part of the Matrix specification and the chosen maximum
  lengths are arbitrary. Not all clients might abide by them. Refer to referenced
  GitHub security advisory for additional details including workarounds.
affected:
- package:
    name: matrix-synapse
    ecosystem: PyPI
    purl: pkg:pypi/matrix-synapse
  ranges:
  - type: ECOSYSTEM
    events:
    - introduced: "0"
    - fixed: 1.28.0
  versions:
  - 0.33.5
  - 0.33.5.1
  - 0.33.6rc1
  - 0.33.6
  - 0.33.7rc1
  - 0.33.7rc2
  - 0.33.7
  - 0.33.8rc2
  - 0.33.8
  - 0.33.9
  - 0.34.0rc1
  - 0.34.0rc2
  - 0.34.0
  - 0.34.0.1
  - 0.34.1.1
  - 0.99.0rc1
  - 0.99.0rc2
  - 0.99.0rc3
  - 0.99.0rc4
  - 0.99.0
  - 0.99.1rc1
  - 0.99.1rc2
  - 0.99.1
  - 0.99.1.1
  - 0.99.2rc1
  - 0.99.2
  - 0.99.3rc1
  - 0.99.3
  - 0.99.3.1
  - 0.99.3.2
  - 0.99.4rc1
  - 0.99.4
  - 0.99.5rc1
  - 0.99.5
  - 0.99.5.1
  - 0.99.5.2
  - 1.0.0rc1
  - 1.0.0rc2
  - 1.0.0rc3
  - 1.0.0
  - 1.1.0rc1
  - 1.1.0rc2
  - 1.1.0
  - 1.2.0rc1
  - 1.2.0rc2
  - 1.2.0
  - 1.2.1
  - 1.3.0rc1
  - 1.3.0
  - 1.3.1
  - 1.4.0rc1
  - 1.4.0rc2
  - 1.4.0
  - 1.4.1rc1
  - 1.4.1
  - 1.5.0rc1
  - 1.5.0rc2
  - 1.5.0
  - 1.5.1
  - 1.6.0rc1
  - 1.6.0rc2
  - 1.6.0
  - 1.6.1
  - 1.7.0rc1
  - 1.7.0rc2
  - 1.7.0
  - 1.7.1
  - 1.7.2
  - 1.7.3
  - 1.8.0rc1
  - 1.8.0
  - 1.9.0.dev1
  - 1.9.0.dev2
  - 1.9.0rc1
  - 1.9.0
  - 1.9.1
  - 1.10.0rc1
  - 1.10.0rc2
  - 1.10.0rc3
  - 1.10.0rc5
  - 1.10.0
  - 1.10.1
  - 1.11.0rc1
  - 1.11.0
  - 1.11.1
  - 1.12.0rc1
  - 1.12.0
  - 1.12.1rc1
  - 1.12.1
  - 1.12.2
  - 1.12.3
  - 1.12.4rc1
  - 1.12.4
  - 1.13.0rc1
  - 1.13.0rc2
  - 1.13.0rc3
  - 1.13.0
  - 1.14.0rc1
  - 1.14.0rc2
  - 1.14.0
  - 1.15.0rc1
  - 1.15.0
  - 1.15.1
  - 1.15.2
  - 1.16.0rc1
  - 1.16.0rc2
  - 1.16.0
  - 1.16.1
  - 1.17.0rc1
  - 1.17.0
  - 1.18.0rc1
  - 1.18.0rc2
  - 1.18.0
  - 1.19.0rc1
  - 1.19.0
  - 1.19.1rc1
  - 1.19.1
  - 1.19.2
  - 1.19.3
  - 1.20.0rc1
  - 1.20.0rc2
  - 1.20.0rc3
  - 1.20.0rc4
  - 1.20.0rc5
  - 1.20.0
  - 1.20.1
  - 1.21.0rc1
  - 1.21.0rc2
  - 1.21.0rc3
  - 1.21.0
  - 1.21.1
  - 1.21.2
  - 1.22.0rc1
  - 1.22.0rc2
  - 1.22.0
  - 1.22.1
  - 1.23.0rc1
  - 1.23.0
  - 1.23.1
  - 1.24.0rc1
  - 1.24.0rc2
  - 1.24.0
  - 1.25.0rc1
  - 1.25.0
  - 1.26.0rc1
  - 1.26.0rc2
  - 1.26.0
  - 1.27.0rc1
  - 1.27.0rc2
  - 1.27.0
  - 1.28.0rc1
references:
- type: WEB
  url: https://github.com/matrix-org/synapse/pull/9321
- type: PACKAGE
  url: https://pypi.org/project/matrix-synapse/
- type: WEB
  url: https://github.com/matrix-org/synapse/pull/9393
- type: ADVISORY
  url: https://github.com/matrix-org/synapse/security/advisories/GHSA-w9fg-xffh-p362
aliases:
- CVE-2021-21394
- GHSA-w9fg-xffh-p362
modified: "2021-04-21T17:02:00Z"
published: "2021-04-12T21:15:00Z"