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Security Advisories: MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLTI0NnctNTZtMi01ODk5

Cross-site scripting (XSS) vulnerability in the password reset endpoint


The password reset 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.


This is fixed in #9200.


Depending on the needs and configuration of the homeserver a few options are available:

  1. Password resets can be disabled by delegating email to a third-party service (via the setting) or disabling email (by not configuring the email setting).

  2. If the homeserver is not configured to use passwords (via the password_config.enabled setting) then the affected endpoint can be blocked at a reverse proxy:

    • /_synapse/client/password_reset/email/submit_token
  3. The password_reset_confirmation.html template can be overridden with a custom template that manually escapes the variables using JInja2's escape filter. See the email.template_dir setting.

Source: GitHub Advisory Database
Origin: Unspecified
Severity: Moderate
Classification: General
Published: over 2 years ago
Updated: 8 months ago

CVSS Score: 6.9
CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:L/A:N

Identifiers: GHSA-246w-56m2-5899, CVE-2021-21332

Affected Packages

Versions: < 1.27.0
Fixed in: 1.27.0