CVE-2021-29474— HedgeDoc 路径遍历漏洞

Relative Path Traversal Attack on note creation

HedgeDoc (formerly known as CodiMD) is an open-source collaborative markdown editor. An attacker can read arbitrary `.md` files from the server's filesystem due to an improper input validation, which results in the ability to perform a relative path traversal. To verify if you are affected, you can try to open the following URL: `http://localhost:3000/..%2F..%2FREADME#` (replace `http://localhost:3000` with your instance's base-URL e.g. `https://demo.hedgedoc.org/..%2F..%2FREADME#`). If you see a README page being rendered, you run an affected version. The attack works due the fact that the internal router passes the url-encoded alias to the `noteController.showNote`-function. This function passes the input directly to findNote() utility function, that will pass it on the the parseNoteId()-function, that tries to make sense out of the noteId/alias and check if a note already exists and if so, if a corresponding file on disk was updated. If no note exists the note creation-function is called, which pass this unvalidated alias, with a `.md` appended, into a path.join()-function which is read from the filesystem in the follow up routine and provides the pre-filled content of the new note. This allows an attacker to not only read arbitrary `.md` files from the filesystem, but also observes changes to them. The usefulness of this attack can be considered limited, since mainly markdown files are use the file-ending `.md` and all markdown files contained in the hedgedoc project, like the README, are public anyway. If other protections such as a chroot or container or proper file permissions are in place, this attack's usefulness is rather limited. On a reverse-proxy level one can force a URL-decode, which will prevent this attack because the router will not accept such a path.

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

输入验证不恰当

HedgeDoc 路径遍历漏洞

HedgeDoc是HedgeDoc团队的一个基于Javascript的Markdown文档实时编辑分享平台。 HedgeDoc 存在路径遍历漏洞，攻击者可以从服务器的文件系统中读取任意的.md文件，从而可以执行相对路径遍历。

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