Mistune before 3.3.0 contains a path traversal vulnerability in the Include directive that allows attackers to read arbitrary files by supplying ../ sequences in include paths. Attackers can also inject HTML through unescaped error messages and included file contents to perform cross-site scripting even when escape=True is set.

Mistune before 3.3.0 contains a path traversal vulnerability in the opt-in Include directive that allows attackers to read local files by supplying relative or absolute include paths. Attackers who submit Markdown rendered via Markdown.read() can disclose files such as /etc/passwd and inject unescaped HTML or script content into rendered output.

Mistune before 3.3.0 contains a path traversal vulnerability in the RST include directive that allows attackers to read arbitrary files by supplying relative or absolute paths. Attackers can submit markdown containing include directives referencing ../ sequences or absolute paths to embed sensitive files like credentials or environment data in rendered HTML.

Mistune before 3.3.0 contains an algorithmic complexity vulnerability in the inline link parser that allows unauthenticated attackers to exhaust CPU by submitting long runs of unmatched '[' characters. Attackers can send small markdown payloads that trigger O(N^2) parselinktext and parselinklabel probing, occupying rendering workers for 30+ seconds per 16 KB input.

Mistune from 3.2.1 before 3.3.0 contains a CSS injection vulnerability that allows attackers controlling markdown input to inject arbitrary style declarations via the unvalidated figwidth option of the figure directive. Attackers can append declarations like background:url() to the rendered figure style attribute, forcing victim browsers to send requests to attacker servers and leak attribute values.

Mistune from 3.0.0 before 3.3.0 contains an algorithmic complexity denial of service vulnerability in the parselinktext function in src/mistune/helpers.py. Attackers can submit markdown with deeply nested square brackets triggering quadratic parsing time, exhausting server CPU with small crafted requests.

Mistune before 3.3.0 contains a cross-site scripting vulnerability in the Include directive that emits included .html, .xhtml, or .htm file content as raw blockhtml tokens. Attackers who can plant an HTML file readable by the renderer can reference it via an include directive, combined with path traversal, to execute stored scripts when escape=False is set.

Mistune from 3.0.0 before 3.3.0 contains an algorithmic complexity vulnerability in the inline link parser's parselinktext function that allows unauthenticated attackers to exhaust CPU with unbalanced brackets. Attackers can submit Markdown containing many unbalanced '[' or '![' characters, forcing repeated unbounded forward scans and tying up worker processes for minutes.

Mistune before 3.3.0 contains an inefficient algorithmic complexity vulnerability in parselinktext that allows remote attackers to cause denial of service through unbalanced square brackets. Attackers can submit markdown containing long runs of unmatched brackets to mistune.html(), triggering repeated forward scans that stall worker processes for minutes.

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, Mistune is vulnerable to a CPU exhaustion DoS due to superlinear (approximately O(n²)) behavior in parselinktext. When parsing Markdown containing many consecutive [ characters, parselinktext repeatedly scans the input using a regex search inside a loop. Each iteration re-scans a large portion of the remaining string, resulting in quadratic-time behavior. An attacker-controlled Markdown input can therefore trigger excessive CPU usage with a very small payload. This vulnerability is fixed in 3.3.0.