PYSEC-2026-663

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Import Source

https://github.com/pypa/advisory-database/blob/main/vulns/matrix-synapse/PYSEC-2026-663.yaml

JSON Data

https://api.osv.dev/v1/vulns/PYSEC-2026-663

Aliases

Published

2026-07-02T14:13:17.409521Z

Modified

2026-07-06T08:00:38.809523599Z

Severity

5.3 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L CVSS Calculator

Summary

Uncontrolled Resource Consumption in Matrix Synapse

Details

Impact

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 (for instance, Icecast).

This can cause excessive traffic and connections toward such servers if their stream URL is, for example, posted to a large room with many Synapse instances with URL preview enabled.

Patches

1.52.0 implements a timeout mechanism which will terminate URL preview connections after 30 seconds. Since generating URL previews for media streams is not supported and always fails, 1.53.0 additionally implements an allow list for content types for which Synapse will even attempt to generate a URL preview.

We recommend upgrading to 1.53.0 to fully resolve the issue.

Workarounds

Turn off URL preview functionality by setting url_preview_enabled: false in the Synapse configuration file.

References

Patch (timeout): https://github.com/matrix-org/synapse/pull/11784
Patch (content type allow list): https://github.com/matrix-org/synapse/pull/11936

For more information

If you have any questions or comments about this advisory, e-mail us at security@matrix.org.

References

Affected packages

PyPI / matrix-synapse

Package

Name: matrix-synapse; View open source insights on deps.dev
Purl: pkg:pypi/matrix-synapse

Affected ranges

Type: ECOSYSTEM
Events: Introduced

0Unknown introduced version / All previous versions are affected

Fixed

1.53.0

Affected versions

0.*

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.*

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

1.28.0

1.29.0rc1

1.29.0

1.30.0rc1

1.30.0

1.30.1

1.31.0rc1

1.31.0

1.32.0rc1

1.32.0

1.32.1

1.32.2

1.33.0rc1

1.33.0rc2

1.33.0

1.33.1

1.33.2

1.34.0rc1

1.34.0

1.35.0rc1

1.35.0rc2

1.35.0rc3

1.35.0

1.35.1

1.36.0rc1

1.36.0rc2

1.36.0

1.37.0rc1

1.37.0

1.37.1rc1

1.37.1

1.38.0rc1

1.38.0rc2

1.38.0rc3

1.38.0

1.38.1

1.39.0rc1

1.39.0rc2

1.39.0rc3

1.39.0

1.40.0rc1

1.40.0rc2

1.40.0rc3

1.40.0

1.41.0rc1

1.41.0

1.41.1

1.42.0rc1

1.42.0rc2

1.42.0

1.43.0rc1

1.43.0rc2

1.43.0

1.44.0rc1

1.44.0rc2

1.44.0rc3

1.44.0

1.45.0rc1

1.45.0rc2

1.45.0

1.45.1

1.46.0rc1

1.46.0

1.47.0rc1

1.47.0rc2

1.47.0rc3

1.47.0

1.47.1

1.48.0rc1

1.48.0

1.49.0rc1

1.49.0

1.49.2

1.50.0rc1

1.50.0rc2

1.50.0

1.50.1

1.50.2

1.51.0rc1

1.51.0rc2

1.51.0

1.52.0rc1

1.52.0

1.53.0rc1

Database specific

source

"https://github.com/pypa/advisory-database/blob/main/vulns/matrix-synapse/PYSEC-2026-663.yaml"