ZEBRA is a Zcash node written entirely in Rust. Prior to zebrad 5.0.0, halo2_gadgets 0.5.0, orchard 0.14.0, zcash_primitives 0.28.0, and zcashd 6.20.0, the variable-base scalar multiplication gadget in halo2_gadgets/src/ecc/chip/mul/incomplete.rs used assign_advice() for the base point without a copy constraint tying it to the actual base, allowing a malicious prover to produce a valid proof for an Orchard Action with an under-constrained base point and bypass the diversified-address-integrity check that binds pk_d, g_d, ivk, the nullifier (nf), and the spend validating key (ak) to the note being spent. This issue is fixed in zebrad 5.0.0, halo2_gadgets 0.5.0, orchard 0.14.0, zcash_primitives 0.28.0, and zcashd 6.20.0.

Zcashd in Zcash before 2.0.7-3 allows discovery of the IP address of a full node that owns a shielded address, related to mishandling of exceptions during deserialization of note plaintexts. This affects anyone who has disclosed their zaddr to a third party.

Zcash 2.x allows an inexpensive approach to "fill all transactions of all blocks" and "prevent any real transaction from occurring" via a "Sapling Wood-Chipper" attack.

Zcash, before the Sapling network upgrade (2018-10-28), had a counterfeiting vulnerability. A key-generation process, during evaluation of polynomials related to a to-be-proven statement, produced certain bypass elements. Availability of these elements allowed a cheating prover to bypass a consistency check, and consequently transform the proof of one statement into an ostensibly valid proof of a different statement, thereby breaking the soundness of the proof system. This misled the original Sprout zk-SNARK verifier into accepting the correctness of a transaction.