Answered by Shaykh Amjad Rasheed
The Shafi’I imams, may Allah be well pleased with them, have mentioned that eating fox and hyena is permissible. Was this ruling based on information that may not have been up-to-date with what we know today, that might show that they were incorrect?

Our imams did not base their saying of the permissibility of eating fox and hyena on contemporary facts, meaning medical or zoological. Rather, they based it on established legal principles and proofs that are established in their relevant sources.
Among these principles is that whatever does not attack with its fangs is halal to eat. The fox and hyena do have fangs, but they are weak, and they don’t attack with them. Tirmidhi related in his authentic chain that the Prophet, may Allah’s peace and blessings be upon him, said about hyena, “It is permissible to eat.” And our imam, Imam al-Shafi’I, may Allah be well pleased with him and have mercy on him, said “People still eat it between Safa and Marwa, without any blame.” Our imams did analogy of the fox with the hyena, because of both have weak fangs, as we mentioned.
الجواب : لم يبنِ أئمتُنا قولَهم بحل أكل الثعلب والضبع على معلومات علمية ؛ بمعنى طبية أو ما يتعلق بتكوين الحيوان ، وإنما بنوا ذلك على قواعدَ وأدلةٍ شرعية قرَّروها معلومةٍ في بابها ، منها : أنَّ ما ليس له نابٌ يَعْدُو به فهو حلالٌ ، والثعلبُ والضبعُ لهما نابٌ لكنَّ نابهما ضعيفٌ لا يَعْدُوان به ، وقد روى الترمذيُّ بسندٍ صحيحٍ أنه صلى الله عليه وسلم قال في الضبع : ” يحلُّ أكله “. وقال إمامُنا الشافعي رضي الله عنه ورحمه :” ما زالَ الناسُ يأكلونها بين الصفا والمروة من غير نكير “. وقاس أئمتنا الثعلب على الضبع بجامع ضعف ناب كلٍّ كما مرَّ .