In RELIC before 2020-08-01, RSA PKCS#1 v1.5 signature forgery can occur because certain checks of the padding (and of the first two bytes) are inadequate. NOTE: this requires that a low public exponent (such as 3) is being used. The product, by default, does not generate RSA keys with such a low number.
https://github.com/relic-toolkit/relic/tree/32eb4c257fc80328061d66639b1cdb35dbed51a2
https://github.com/relic-toolkit/relic/commit/76c9a1fdf19d9e92e566a77376673e522aae9f80