Electrum before 4.7.2 Nostr Wallet Connect Plugin Daily Spending Limit Bypass

Summary

Electrum before 4.7.2 contains a spending limit bypass vulnerability in the Nostr Wallet Connect plugin that allows malicious NWC clients to exceed daily_limit_sat by exploiting non-atomic budget checks and millisatoshi truncation. Attackers can send concurrent pay_invoice requests that pass budget_allows_spend() before add_to_budget() runs, or repeatedly pay msat amounts that are floored to whole satoshis, to drain funds beyond the limit.

Remediation

1. Inventory every spesmilo electrum deployment, including staging.
2. Upgrade spesmilo electrum to 4.7.2.
3. Confirm the running version after the upgrade.

References

• Patchhttps://github.com/spesmilo/electrum/commit/5222374046d2a92da371d46c79ce0e61e7e2a42d
• Patchhttps://github.com/spesmilo/electrum/commit/3956bff0684f6060fbe8c823c3ee921928cdcaa5
• Advisoryhttps://github.com/spesmilo/electrum/security/advisories/GHSA-q7m2-785w-r585
• Advisoryhttps://www.vulncheck.com/advisories/electrum-before-4.7.2-nostr-wallet-connect-plugin-daily-spending-limit-bypass