GHSA-8q93-326v-3m7g

Source

https://github.com/advisories/GHSA-8q93-326v-3m7g

Import Source

https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-8q93-326v-3m7g/GHSA-8q93-326v-3m7g.json

JSON Data

https://api.osv.dev/v1/vulns/GHSA-8q93-326v-3m7g

Aliases

Downstream

CGA-37wq-rjw3-2r69

CGA-f5m9-whwm-vwxm

Published

2026-05-14T16:18:40Z

Modified

2026-09-10T03:51:04Z

Severity

5.5 (Medium) CVSS_V3 - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H CVSS Calculator
7.1 (High) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N CVSS Calculator

Summary

Synapse CPU starvation (Denial of Service)

Details

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 to limit the rate of user requests, preventing or increasing the difficulty of the attack.

Identifiers

ELEMENTSEC-2026-1706

For more information

If you have any questions or comments about this advisory, please email us at security at element.io.

Database specific

{
    "cwe_ids": [
        "CWE-400",
        "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-14T16:18:40Z",
    "nvd_published_at": "2026-05-28T17:16:31Z",
    "severity": "HIGH"
}

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

0 Unknown introduced version / All previous versions are affected

Fixed

1.152.1

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

1.53.0

1.54.0rc1

1.54.0

1.55.0rc1

1.55.0

1.55.1

1.55.2

1.56.0rc1

1.56.0

1.57.0rc1

1.57.0

1.57.1

1.58.0rc2

1.58.0

1.58.1

1.59.0rc1

1.59.0rc2

1.59.0

1.59.1

1.60.0rc1

1.60.0rc2

1.60.0

1.61.0rc1

1.61.0

1.61.1

1.62.0rc1

1.62.0rc2

1.62.0rc3

1.62.0

1.63.0rc1

1.63.0

1.63.1

1.64.0rc1

1.64.0rc2

1.64.0

1.65.0rc1

1.65.0rc2

1.65.0

1.66.0rc1

1.66.0rc2

1.66.0

1.67.0rc1

1.67.0

1.68.0rc1

1.68.0rc2

1.68.0

1.69.0rc1

1.69.0rc2

1.69.0rc4

1.69.0

1.70.0rc1

1.70.0rc2

1.70.0

1.70.1

1.71.0rc1

1.71.0rc2

1.71.0

1.72.0rc1

1.72.0

1.73.0rc2

1.73.0

1.74.0rc1

1.74.0

1.75.0rc1

1.75.0rc2

1.75.0

1.76.0rc1

1.76.0rc2

1.76.0

1.77.0rc1

1.77.0rc2

1.77.0

1.78.0rc1

1.78.0

1.79.0rc1

1.79.0rc2

1.79.0

1.80.0rc1

1.80.0rc2

1.80.0

1.81.0rc1

1.81.0rc2

1.81.0

1.82.0rc1

1.82.0

1.83.0rc1

1.83.0

1.84.0rc1

1.84.0

1.84.1

1.85.0rc1

1.85.0rc2

1.85.0

1.85.1

1.85.2

1.86.0rc2

1.86.0

1.87.0rc1

1.87.0

1.88.0rc1

1.88.0

1.89.0rc1

1.89.0

1.90.0rc1

1.90.0

1.91.0rc1

1.91.0

1.91.1

1.91.2

1.92.0rc1

1.92.1

1.92.2

1.92.3

1.93.0rc1

1.93.0

1.94.0rc1

1.94.0

1.95.0rc1

1.95.0

1.95.1

1.96.0rc1

1.96.1

1.97.0rc1

1.97.0

1.98.0rc1

1.98.0

1.99.0rc1

1.99.0

1.100.0rc2

1.100.0rc3

1.100.0

1.101.0rc1

1.101.0

1.102.0rc1

1.102.0

1.103.0rc1

1.103.0

1.104.0rc1

1.104.0

1.105.0rc1

1.105.0

1.105.1

1.106.0rc1

1.106.0

1.107.0rc1

1.107.0

1.108.0rc1

1.108.0

1.109.0rc1

1.109.0rc2

1.109.0rc3

1.109.0

1.110.0rc2

1.110.0rc3

1.110.0

1.111.0rc1

1.111.0rc2

1.111.0

1.111.1

1.112.0rc1

1.112.0

1.113.0rc1

1.113.0

1.114.0rc1

1.114.0rc3

1.114.0

1.115.0rc1

1.115.0rc2

1.115.0

1.116.0rc1

1.116.0rc2

1.116.0

1.117.0rc1

1.117.0

1.118.0rc1

1.118.0

1.119.0rc2

1.119.0

1.120.0rc1

1.120.0

1.120.2

1.121.0rc1

1.121.0

1.121.1

1.122.0rc1

1.122.0

1.123.0rc1

1.123.0

1.124.0rc1

1.124.0rc2

1.124.0rc3

1.124.0

1.125.0rc1

1.125.0

1.126.0rc2

1.126.0rc3

1.126.0

1.127.0rc1

1.127.0

1.127.1

1.128.0rc1

1.128.0

1.129.0rc2

1.129.0

1.130.0rc1

1.130.0

1.131.0rc1

1.131.0

1.132.0rc1

1.132.0

1.133.0rc1

1.133.0

1.134.0rc1

1.134.0

1.135.0rc1

1.135.0rc2

1.135.0

1.135.2

1.136.0rc1

1.136.0rc2

1.136.0

1.137.0rc1

1.137.0

1.138.0rc1

1.138.0

1.138.2

1.138.3

1.138.4

1.139.0rc2

1.139.0rc3

1.139.0

1.139.1

1.139.2

1.140.0rc1

1.140.0

1.141.0rc1

1.141.0rc2

1.141.0

1.142.0rc3

1.142.0rc4

1.142.0

1.142.1

1.143.0rc2

1.143.0

1.144.0rc1

1.144.0

1.145.0rc1

1.145.0rc2

1.145.0rc3

1.145.0rc4

1.145.0

1.146.0rc1

1.146.0

1.147.0rc1

1.147.0

1.147.1

1.148.0rc1

1.148.0

1.149.0rc1

1.149.0

1.149.1

1.150.0rc1

1.150.0

1.151.0rc1

1.151.0

1.152.0rc1

1.152.0

Database specific

source

"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-8q93-326v-3m7g/GHSA-8q93-326v-3m7g.json"