  Despite the impressive success of the standard cosmological model, several
anomalies defy its triumph. Among them is the so-called lensing anomaly: the
Planck satellite observes stronger CMB gravitational lensing than expected. The
role of neutrinos in this anomaly has been mostly overlooked, despite their key
role in CMB lensing, because in the standard scenario they tend to increase the
tension. Here, we show that this strongly depends on the assumed neutrino
equation of state. We demonstrate that if neutrinos have yet undiscovered
long-range interactions, the lensing pattern is significantly affected,
rendering the lensing anomaly as a statistical fluctuation. Our results thus
open up a window to link anomalous CMB lensing with present and future
cosmological, astrophysical, and laboratory measurements of neutrino
properties.
