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GHSA-246w-56m2-5899

MediumCVSS 6.9 / 10
Published Mar 26, 2021·Last modified Mar 13, 2026
Affected Components(0)

No affected components available

Description

Impact

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.

Patches

This is fixed in #9200.

Workarounds

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 account_threepid_delegates.email 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.

Risk Scores
Base Score
6.9

The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The vulnerability can affect other systems as well, not just the initial system. There is a high impact on the confidentiality of the information. There is a low impact on the integrity of the data.

Threat Intelligence
6.3

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
1.22%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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Medium severity
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