Heap-based buffer overflow in the ParseValue function in lexer.c in tidy before 4.9.31 allows remote attackers to cause a denial of service (crash) via vectors involving a command character in an href.

The ParseValue function in lexer.c in tidy before 4.9.31 allows remote attackers to cause a denial of service (crash) via vectors involving multiple whitespace characters before an empty href, which triggers a large memory allocation.

In Tidy 5.5.31, the IsURLCodePoint function in attrs.c allows attackers to cause a denial of service (Segmentation Fault), as demonstrated by an invalid ISALNUM argument.

In Tidy 5.7.0, the prvTidyTidyMetaCharset function in clean.c allows attackers to cause a denial of service (Segmentation Fault), because the currentNode variable in the "children of the head" processing feature is modified in the loop without validating the new value.