The Bitcoin Core development team has publicly disclosed a medium-risk security vulnerability, identified as CVE-2025-62860, which could allow external incoming connections via the Tor network to bypass standard security restrictions. According to a security advisory released on November 10, 2026, the flaw involves the accidental granting of whitelist permissions to untrusted nodes. While the bug does not lead to a loss of funds, it compromises the anti-DoS (Denial-of-Service) limitations and privacy leak mitigation measures that are otherwise active for standard network participants.
Mechanism of the Whitelist Permission Flaw
The vulnerability stems from how Bitcoin Core interprets IP addresses when receiving traffic through the Tor onion service. When a node accepts incoming connections via a local Tor daemon, the source IP address often appears as the address of the local Tor software itself. If a node operator has configured the -whitelist option to include their own local network range, the software may mistakenly identify external Tor connections as trusted internal nodes.
This misidentification occurs because the software fails to differentiate between a legitimate local administrative connection and an external peer connecting through the Tor proxy service.
Impacted versions and configurations include:
- Bitcoin Core versions prior to 28.3, 29.2, and 30.0.
- Nodes utilizing the non-default -whitelist configuration.
- Implementations where vendors bundle the Tor daemon with pre-configured whitelist settings.
Security Implications and Mitigation Strategies
The primary risk associated with this vulnerability is the potential for an attacker to exhaust node resources. By gaining whitelist permissions, an external actor can bypass the rate limits and protection mechanisms designed to prevent network abuse. Furthermore, the advisory notes that nodes not using the specific -whitelist flag remain unaffected by this particular security flaw.
Due to incoming connections from external sources via Tor, the IP address is effectively the address of the local Tor software. If this address matches the trusted IP range... Bitcoin Core will mistakenly whitelist these external Tor connections.
To address this issue, node operators are encouraged to update their software to the patched versions (28.3, 29.2, or 30.0) immediately. These updates implement stricter verification for incoming Tor traffic to ensure that external peers are not granted elevated privileges.
In conclusion, while CVE-2025-62860 is categorized as a medium-risk threat, it highlights the complexities of maintaining privacy-centric connections within the Bitcoin ecosystem. Ensuring that blockchain infrastructure remains resilient against such misconfigurations is vital for the long-term stability of the network, particularly for operators who rely on Tor for enhanced anonymity.
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