md_analyze_line in md4c.c in md4c 0.4.7 allows attackers to trigger use of uninitialized memory, and cause a denial of service via a malformed Markdown document.

md_push_block_bytes in md4c.c in md4c 0.4.5 allows attackers to trigger use of uninitialized memory, and cause a denial of service (e.g., assertion failure) via a malformed Markdown document.

md_build_attribute in md4c.c in md4c 0.2.6 allows remote attackers to cause a denial of service (Segmentation fault and application crash) or possibly have unspecified other impact via a crafted file.

md4c 0.2.6 has a NULL pointer dereference in the function md_process_line in md4c.c, related to ctx->current_block.

md_is_link_reference_definition_helper in md4c 0.2.5 has a heap-based buffer over-read because md_is_link_label mishandles loop termination.

md4c 0.2.5 has a heap-based buffer over-read because md_is_named_entity_contents has an off-by-one error.

md4c 0.2.5 has a heap-based buffer overflow in md_merge_lines because md_is_link_label mishandles the case of a link label composed solely of backslash escapes.

md4c before 0.2.5 has a heap-based buffer overflow because md_split_simple_pairing_mark mishandles splits.