<p>It turns out that in fact <strong>all</strong> of the peers can be Byzantine (same for the clients as well).</p>

<p>This is precisely stated in the <a href="https://arxiv.org/pdf/1801.10228.pdf" rel="nofollow noreferrer">Hyperledger Fabric: A Distributed Operating System  for Permissioned Blockchains</a> paper, section 3.5 (Trust and Fault Model). The integrity of HLF relies <strong>solely</strong> on the orderers. This is because even if all peers collude and try to rewrite history in the blockchain, they won't be able to produce signed blocks (as the orderers are the only entities that can make blocks). </p>

<p>The best they can do is to try to delete blocks, but even with the presence of a <em>single</em> honest peer, that peer will show a "longer" history of blocks which will be the accepted one.</p>
Hyperledger Fabric blockchain reorganization or fork
<p>This is a more theoretical question than a practical one, but I was thinking on possible attacks in Hyperledger Fabric.</p>

<p>On a high level, orderers are the block makers, and the whole blockchain is eventually maintained by the peers. The consensus algorithm is executed among the orderers (which might tolerate up to a certain number of byzantine orderers if the consensus is byzantine fault tolerant). </p>

<p>But what happens if some peers are compromised? What would happen if an attacker subverts more than half of the peers in the system? Could it result in a chain fork or reorganization?</p>