Grading: Its chain is "ruined" (talif) because of Sayf bin Muhammad (al-Thawri), for he is "matruk", and indeed accused of lying and fabricating hadith.
Technical note / Defect ('illah): Abd al-Razzaq al-San'ani contradicted him (in Ibn Abi 'Asim's "al-Awa'il" 67, and al-Tabarani's "al-Kabir" 6174 and "al-Awa'il" 51): he narrated it from Sufyan al-Thawri, from Salamah bin Kuhayl, from Abu Sadiq, from 'Ulaym al-Kindi, from Salman as "mawquf" (a saying of the Companion). So he mentioned 'Ulaym al-Kindi in place of al-Agharr, and made it mawquf on Salman. However, Abu al-Salt Abd al-Salam bin Salih narrated it from Abd al-Razzaq as marfu' (attributed to the Prophet) (in Ibn Abi Khaythamah's "Tarikh", third part, 379, Ibn al-A'rabi's "Mu'jam" 1298, and Ibn al-Maghazili's "Manaqib Ali" 22), but those of Abd al-Razzaq's students who made it mawquf on Salman are more trustworthy and more eminent than Abd al-Salam bin Salih. Yahya bin Yaman agreed with them (in Ibn 'Asakir's "Tarikh Dimashq" 42/ 40), narrating it from Sufyan al-Thawri with the mention of 'Ulaym and as mawquf. Likewise Qays bin al-Rabi' (in Ibn Abi Shaybah 12/ 76 and 14/ 121) and Shu'ayb bin Khalid al-Razi (in Abd al-Ghani bin Sa'id al-Misri's "Idah al-Ishkal", as in al-Suyuti's "al-La'ali' al-Masnu'ah" 1/ 300) narrated it from Salamah bin Kuhayl with the mention of 'Ulaym al-Kindi and as mawquf.

Technical note / Defect ('illah): All of them were contradicted by Yahya bin Hashim bin Kathir al-Ghassani (in al-Harith bin Abi Usamah, as in al-Haythami's "Bughyat al-Bahith" 980, and Ibn 'Abd al-Barr's "al-Isti'ab" p. 523 and "al-Tamhid" 2/ 305): he narrated it from Sufyan al-Thawri, from Salamah bin Kuhayl, from Abu Sadiq, from Hanash bin al-Mu'tamir, from 'Ulaym al-Kindi, from Salman, as "marfu'". But this Yahya bin Hashim is accused of lying. He was not alone in it, however: al-Fadl bin al-Fadl Abu 'Ubaydah al-Basri also narrated it (in Abu al-Fath al-Azdi's "Man Wafaqa Ismuhu Ism Abihi" 70), but this al-Fadl bin al-Fadl is "layyin al-hadith" (weak).

General principle: So the most likely of all these is the narration of those who narrated it from Salamah bin Kuhayl, from Abu Sadiq, from 'Ulaym al-Kindi, from Salman as mawquf. This 'Ulaym is of unknown status (jahalah), and he is alone in narrating it, so it is not authentic. In that case there is no place for the statement of Ibn 'Abd al-Barr in "al-Isti'ab" and al-Suyuti in "al-La'ali'" that "despite being mawquf it has the ruling of marfu', because it cannot be known by opinion". That applies only when the chain is authentic, which is not the case here. And Allah the Exalted knows best.