How sound is the chain of narration for the story of the woman who vowed to slaughter her son at the Kaaba, and the details of her seeking fatwas from Ibn Umar and Ibn Abbas, and Marwan's statement concerning it, and is this narration a mursal hadith?

No one has weakened this narration, nor has anyone mentioned the impossibility of Qabisah narrating from Ibn Umar, Marwan, and Ibn Abbas. Qabisah was born in the year of the Conquest and resided in Medina before moving to Damascus. The other narrators in the chain are narrators found in authentic collections. Sheikh al-Islam and Al-Dhahabi mentioned the narration and did not criticize its chain. Sheikh al-Islam and others affirmed what the narration implied regarding not fulfilling a vow of disobedience. This is supported by the hadith in Al-Bukhari: "Whoever vows to disobey Allah, he should not disobey Him," and the hadith in Muslim: "There is no vow in disobedience to Allah, nor in what the son of Adam does not possess."