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

Electrum 4.6.0 before 4.7.2 contains an authorization bypass in the external plugin loader, which executes a plugin's init.py module when the plugin is marked enabled in the config file, without verifying its plugin-password signature. A rogue local process with write access to the Electrum data directory can place plugin code in the plugins/ folder and mark it enabled, causing arbitrary code execution inside the Electrum process.

Electrum before 4.8.3 fails to verify signatures of wallet-owned inputs in unconfirmed mempool transactions, allowing malicious servers to replace a just-broadcast transaction with a conflicting one. Attackers can swallow the user's transaction and display an invalid zero-fee copy paying an attacker address, tricking users into RBF fee-bumping and signing it.

paymentrequest.py in Electrum before 4.2.2 allows a file:// URL in the r parameter of a payment request (e.g., within QR code data). On Windows, this can lead to capture of credentials over SMB. On Linux and UNIX, it can lead to a denial of service by specifying the /dev/zero filename.

Electrum Technologies GmbH Electrum Bitcoin Wallet version prior to version 3.0.5 contains a Missing Authorization vulnerability in JSONRPC interface that can result in Bitcoin theft, if the user's wallet is not password protected. This attack appear to be exploitable via The victim must visit a web page with specially crafted javascript. This vulnerability appears to have been fixed in 3.0.5.

The Python console in Electrum through 2.9.4 and 3.x through 3.0.5 supports arbitrary Python code without considering (1) social-engineering attacks in which a user pastes code that they do not understand and (2) code pasted by a physically proximate attacker at an unattended workstation, which makes it easier for attackers to steal Bitcoin via hook code that runs at a later time when the wallet password has been entered, a different vulnerability than CVE-2018-1000022.