According to CoinMeta, a security announcement for Bitcoin Core indicates that a medium-risk vulnerability CVE-2025-62859 was disclosed on November 10, 2026, and it exists in versions prior to 29.2 and 30.0. Malicious nodes can exploit the witness data within compact blocks to tamper with them, causing the processing of victims' blocks to be stalled under certain conditions. Affected nodes will clear their download status after rebuilding compact blocks but before checking the witness data. If the check fails, the node will revert to requesting complete blocks from the same node and wait for a 10-minute timeout. If the attacker controls three high-bandwidth peer nodes of the victim, or if the victim is running in - blockonly mode, this attack can be repeated indefinitely.