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CVE-2021-29471: Denial of service attack via push rule patterns in matrix-synapse

May 13, 2021 (updated September 30, 2024)

“Push rules” can specify conditions under which they will match, including event_match, which matches event content against a pattern including wildcards.

Certain patterns can cause very poor performance in the matching engine, leading to a denial-of-service when processing moderate length events.

References

  • github.com/advisories/GHSA-x345-32rc-8h85
  • github.com/matrix-org/synapse
  • github.com/matrix-org/synapse/commit/03318a766cac9f8b053db2214d9c332a977d226c
  • github.com/matrix-org/synapse/releases/tag/v1.33.2
  • github.com/matrix-org/synapse/security/advisories/GHSA-x345-32rc-8h85
  • github.com/pypa/advisory-database/tree/main/vulns/matrix-synapse/PYSEC-2021-135.yaml
  • lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY
  • nvd.nist.gov/vuln/detail/CVE-2021-29471

Code Behaviors & Features

Detect and mitigate CVE-2021-29471 with GitLab Dependency Scanning

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Affected versions

All versions before 1.33.2

Fixed versions

  • 1.33.2

Solution

Upgrade to version 1.33.2 or above.

Impact 5.3 MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Learn more about CVSS

Weakness

  • CWE-331: Insufficient Entropy
  • CWE-400: Uncontrolled Resource Consumption

Source file

pypi/matrix-synapse/CVE-2021-29471.yml

Spotted a mistake? Edit the file on GitLab.

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