The vulnerability in mdex involves two mutually recursive Rust functions, ex_document_to_comrak_ast and comrak_ast_to_ex_document, which convert between Elixir %MDEx.Document{} structs and Comrak's internal AST. These functions do not limit recursion depth, allowing an attacker to supply Markdown documents with thousands of nested block quotes. This unbounded recursion causes a stack overflow in the native code, resulting in an uncatchable SIGSEGV inside a NIF (Native Implemented Function). The Erlang runtime cannot contain this fault, causing the entire BEAM process to terminate and killing all Elixir and Erlang processes on the node. The vulnerability affects mdex versions >=0.3.0 and <0.12.3 and mdex_native versions >=0.1.0 and <0.2.3. There is no indication of a vendor-provided patch or remediation level in the provided data.

Exploitation of this vulnerability allows an attacker to cause a denial of service by crashing the BEAM virtual machine process hosting Elixir and Erlang applications. This results in a complete termination of all running processes on the node, not just the one processing the malicious Markdown input. No authentication or special privileges are required, increasing the risk of exploitation in environments where untrusted Markdown input is rendered.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, avoid rendering untrusted Markdown input with affected versions of mdex and mdex_native. Consider implementing input validation or limiting Markdown nesting depth externally if possible. Monitor vendor channels for updates regarding patches or official mitigations.