Bitcoin Core Discloses Medium-Severity Vulnerability That Can Cause Block Processing to Stall

Bitcoin Core disclosed a medium-severity vulnerability, CVE-2025-62859, on November 10 that can stall block processing on affected nodes through witness-data tampering in compact blocks. When the tampered check fails, nodes re-request the block from the same peer and wait out a 10-minute timeout, and the attack can repeat indefinitely if the attacker controls three of the victim's high-bandwidth peers or the node runs in blocksonly mode. The flaw affects versions prior to 29.2 and 30.0, with fixes released in 30.0 on October 10, 2025, and in 29.2 on October 14, 2025. The disclosure matters because it highlights a peer-level denial-of-service risk that could slow block propagation for unpatched nodes without requiring a consensus change. Node operators should verify they are running 29.2 or 30.0 or later, and watch for further analysis of how often the three-peer condition occurs in practice.