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Security Advisories: MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLTN4OGMtZm1wYy01cm1x
Cross-site scripting (XSS) vulnerability in the fallback authentication endpoint
Impact
The fallback authentication endpoint served via Synapse was vulnerable to cross-site scripting (XSS) attacks. The impact depends on the configuration of the domain that Synapse is deployed on, but may allow access to cookies and other browser data, CSRF vulnerabilities, and access to other resources served on the same domain or parent domains.
Patches
This is fixed by #8444, which is included in Synapse v1.21.0.
Workarounds
If the homeserver is not configured to use reCAPTCHA, consent (terms of service), or single sign-on then the affected endpoint can be blocked at a reverse proxy:
/_matrix/client/r0/auth/.*/fallback/web/_matrix/client/unstable/auth/.*/fallback/web
JSON: https://advisories.ecosyste.ms/api/v1/advisories/MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLTN4OGMtZm1wYy01cm1x
Source: GitHub Advisory Database
Origin: Unspecified
Severity: Moderate
Classification: General
Published: about 4 years ago
Updated: about 2 months ago
CVSS Score: 6.1
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Identifiers: GHSA-3x8c-fmpc-5rmq, CVE-2020-26891
References:
- https://github.com/matrix-org/synapse/security/advisories/GHSA-3x8c-fmpc-5rmq
- https://github.com/matrix-org/synapse/pull/8444
- https://nvd.nist.gov/vuln/detail/CVE-2020-26891
- https://github.com/matrix-org/synapse/releases
- https://matrix.org/blog/2020/10/15/synapse-1-21-2-released-and-security-advisory
- https://github.com/matrix-org/synapse/releases/tag/v1.21.2
- https://github.com/pypa/advisory-database/tree/main/vulns/matrix-synapse/PYSEC-2020-238.yaml
- https://github.com/advisories/GHSA-3x8c-fmpc-5rmq
Blast Radius: 8.6
Affected Packages
pypi:matrix-synapse
Dependent packages: 6Dependent repositories: 26
Downloads: 99,550 last month
Affected Version Ranges: < 1.21.0
Fixed in: 1.21.0
All affected versions: 0.33.5, 0.33.6, 0.33.7, 0.33.8, 0.33.9, 0.34.0, 0.99.0, 0.99.1, 0.99.2, 0.99.3, 0.99.4, 0.99.5, 1.0.0, 1.1.0, 1.2.0, 1.2.1, 1.3.0, 1.3.1, 1.4.0, 1.4.1, 1.5.0, 1.5.1, 1.6.0, 1.6.1, 1.7.0, 1.7.1, 1.7.2, 1.7.3, 1.8.0, 1.9.0, 1.9.1, 1.10.0, 1.10.1, 1.11.0, 1.11.1, 1.12.0, 1.12.1, 1.12.2, 1.12.3, 1.12.4, 1.13.0, 1.14.0, 1.15.0, 1.15.1, 1.15.2, 1.16.0, 1.16.1, 1.17.0, 1.18.0, 1.19.0, 1.19.1, 1.19.2, 1.19.3, 1.20.0, 1.20.1
All unaffected versions: 1.21.0, 1.21.1, 1.21.2, 1.22.0, 1.22.1, 1.23.0, 1.23.1, 1.24.0, 1.25.0, 1.26.0, 1.27.0, 1.28.0, 1.29.0, 1.30.0, 1.30.1, 1.31.0, 1.32.0, 1.32.1, 1.32.2, 1.33.0, 1.33.1, 1.33.2, 1.34.0, 1.35.0, 1.35.1, 1.36.0, 1.37.0, 1.37.1, 1.38.0, 1.38.1, 1.39.0, 1.40.0, 1.41.0, 1.41.1, 1.42.0, 1.43.0, 1.44.0, 1.45.0, 1.45.1, 1.46.0, 1.47.0, 1.47.1, 1.48.0, 1.49.0, 1.49.2, 1.50.0, 1.50.1, 1.50.2, 1.51.0, 1.52.0, 1.53.0, 1.54.0, 1.55.0, 1.55.1, 1.55.2, 1.56.0, 1.57.0, 1.57.1, 1.58.0, 1.58.1, 1.59.0, 1.59.1, 1.60.0, 1.61.0, 1.61.1, 1.62.0, 1.63.0, 1.63.1, 1.64.0, 1.65.0, 1.66.0, 1.67.0, 1.68.0, 1.69.0, 1.70.0, 1.70.1, 1.71.0, 1.72.0, 1.73.0, 1.74.0, 1.75.0, 1.76.0, 1.77.0, 1.78.0, 1.79.0, 1.80.0, 1.81.0, 1.82.0, 1.83.0, 1.84.0, 1.84.1, 1.85.0, 1.85.1, 1.85.2, 1.86.0, 1.87.0, 1.88.0, 1.89.0, 1.90.0, 1.91.0, 1.91.1, 1.91.2, 1.92.1, 1.92.2, 1.92.3, 1.93.0, 1.94.0, 1.95.0, 1.95.1, 1.96.1, 1.97.0, 1.98.0, 1.99.0, 1.100.0, 1.101.0, 1.102.0, 1.103.0, 1.104.0, 1.105.0, 1.105.1, 1.106.0, 1.107.0, 1.108.0, 1.109.0, 1.110.0, 1.111.0, 1.111.1, 1.112.0, 1.113.0, 1.114.0, 1.115.0, 1.116.0, 1.117.0, 1.118.0