True, but extremely rare, and like most vaccine side effects, much more common following INFECTION than vaccination.
Association of Cerebral Venous Thrombosis with mRNA COVID-19 Vaccines: A Disproportionality Analysis of the World Health Organization Pharmacovigilance Database
https://www.mdpi.com/2076-393X/10/5/799/htm (2022-05-18)
This paper finds that there is an association between vaccination and CVT
"the incidence rate ratio of CVT requiring hospitalization within 6 weeks of SARS-CoV-2 infection was 32 times higher compared with after mRNA-based SARS-CoV-2 vaccination."
https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2790206 (2022-03-17)
"The incidence of CVT and PVT is significantly increased after COVID-19 [compared to after vaccination]. The data highlight the risk of serious thrombotic events in COVID-19 and can help contextualize the risks and benefits of vaccination in this regard."
https://osf.io/a9jdq/ (2021-04-26)
"COVID-19 increasesthe risk of CVT and PVT compared to patients diagnosed with influenza,andto people who have received aCOVID-19 mRNA vaccine."
https://osf.io/a9jdq/ (2021-04-26)
"COVID-19 is associated with a markedly increased incidence of CVT compared to patients with influenza, people who have received BNT162b2 or mRNA-1273 vaccines and compared to the best estimates of the general population incidence."
https://www.thelancet.com/journals/eclinm/article/PIIS2589-5370(21)00341-2/fulltext (2021-07-31)