A range of quadratic parsing issues from cmark/cmark-gfm are also present in Comrak. These can be used to craft denial-of-service attacks on services that use Comrak to parse Markdown.
comrak is vulnerable to the upstream cmark issue, "Issue revealed by fuzzer". A large number of references in a markdown document can trigger an overly large response.
A Comrak AST can be constructed manually by a program instead of parsing a Markdown document with parse_document. This AST can then be converted to HTML via html::format_document_with_plugins. However, the HTML formatting code assumes that the AST is well-formed. For example, many AST notes contain [u8] fields which the formatting code assumes is valid UTF-8 data. Several bugs can be triggered if this is not the case.
An issue was discovered in the comrak crate before 0.10.1 for Rust. It mishandles & characters, leading to XSS via &# HTML entities.
An issue was discovered in the comrak crate before 0.9.1 for Rust. Cross site scripting (XSS) can occur because the protection mechanism for data: and javascript: URIs is case-sensitive, allowing (for example) Data: to be used in an attack.