CERN Indico before 2.3.4 can use an attacker-supplied Host header in a password reset link.

Affected: PyPI: indico

### Impact An external audit of the Indico codebase has discovered a vulnerability in Indico's URL generation logic which could have allowed an attacker to make Indico send a password reset link with a valid token pointing to an attacker-controlled domain by sending that domain in the `Host` header. Had a user clicked such a link without realizing it does not point to Indico (and that they never requested it), it would have revealed their password reset token to the attacker, allowing them to reset the password for that user and thus take over their Indico account.

- If the web server already enforces a canonical host name, this cannot be exploited (this was not part of the default config from the Indico setup guide) - If only SSO is used ([`LOCAL_IDENTITIES`](https://docs.getindico.io/en/stable/config/settings/#LOCAL_IDENTITIES) set to `False`), the vulnerability cannot be exploited for password reset links, but other links in emails set by Indico could be tampered with in the same way (with less problematic impact though)

### Patches You need to update to [Indico 2.3.4](https://github.com/indico/indico/releases/tag/v2.3.4) as soon as possible. See [the docs](https://docs.getindico.io/en/stable/installation/upgrade/) for instructions on how to update.

### Workarounds You can configure the web server to canonicalize the URL to the hostname used for Indico. See [this commit](https://github.com/indico/indico/pull/4815/commits/b6bff6d004abcf07db1891e26a0eb4aa0edb7c21) for th…

Affected: PyPI: indico

CERN Indico before 2.3.4 can use an attacker-supplied Host header in a password reset link.