Sayyiduna Abu Waqid al-Laythi (may Allah be pleased with him) says that the Companions said: O Messenger of Allah (peace and blessings be upon him)! We are in a land where hunger afflicts us; when is carrion lawful for us? He (peace and blessings be upon him) said: "When you find neither morning nor evening food, nor vegetables, then eating carrion is permissible for you."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19636