Bitcoin Core Discloses Medium-Risk Vulnerability That Could Halt Block Processing

ChainCatcher report: According to the Bitcoin Core security advisory, the medium-severity vulnerability CVE-2025-62859 was disclosed on November 10, 2026. This vulnerability affects versions prior to 29.2 and 30, where a malicious node can exploit witness malleation in compact blocks to stall block processing on affected nodes under specific conditions. The advisory notes that affected nodes clear their download state after reconstructing a compact block but before verifying the witness data. If verification fails, the node reverts to requesting the full block from the same peer and waits for a 10-minute timeout. If an 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. The vulnerability was discovered and responsibly disclosed by Eugene Siegel, and a fix has been included in Bitcoin Core versions 29.2 and 30.