URL deny list bypass via oEmbed and image URLs when generating previews in Synapse

Synapse is a Matrix protocol homeserver written in Python with the Twisted framework. A discovered oEmbed or image URL can bypass the `url_preview_url_blacklist` setting potentially allowing server side request forgery or bypassing network policies. Impact is limited to IP addresses allowed by the `url_preview_ip_range_blacklist` setting (by default this only allows public IPs) and by the limited information returned to the client: 1. For discovered oEmbed URLs, any non-JSON response or a JSON response which includes non-oEmbed information is discarded. 2. For discovered image URLs, any non-image response is discarded. Systems which have URL preview disabled (via the `url_preview_enabled` setting) or have not configured a `url_preview_url_blacklist` are not affected. This issue has been addressed in version 1.85.0. Users are advised to upgrade. User unable to upgrade may also disable URL previews.

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N

授权机制不正确

Matrix Synapse 代码问题漏洞

Matrix Synapse是英国Matrix基金会的一款矩阵管理服务器的实现。 Matrix Synapse 1.85.0之前版本存在代码问题漏洞，该漏洞源于通过oEmbed 或URL 可以绕过 url_preview_url_blacklist 设置。

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