CVE-2023-7346

Vulnerability

The Ledger Bitcoin app versions 2.1.0 and 2.1.1, which added miniscript support in February 2023, incorrectly implement the a: fragment used in miniscript policies [1], [2]. This improper handling causes the app to derive and display incorrect Bitcoin receiving addresses when such policies are processed. The vulnerability is classified as CWE-682 (Incorrect Calculation) [2]. Affected users are those who interact with miniscript policies containing the a: fragment; policies without this fragment or wallets not using miniscript are not impacted [1].

Exploitation

An attacker can craft a malicious miniscript policy that includes the a: fragment and present it to the Ledger device [1]. The attacker does not need physical access to the device but must induce the user to use a software wallet that processes such policies. The device then derives and displays a wrong recipient address. The complexity is elevated due to the need for user interaction (e.g., importing a malicious policy) and physical proximity (local or same network) [2]. No prior authentication is required beyond controlling the input to the wallet software [2].

Impact

If exploited, the user may see an incorrect Bitcoin address on the Ledger device screen and approve a transaction destined for that address [1]. This could cause funds to be sent to an unintended address controlled by the attacker, resulting in financial loss. The CVSS v4 score is 4.0 (Medium) with high integrity impact but no confidentiality or availability impact [2]. The limited real-world exposure stems from the fact that no widely deployed wallet software has full miniscript integration [1].

Mitigation

The issue is fixed in Ledger Bitcoin app version 2.1.2, released on an undisclosed date [1]. Users employing miniscript policies should upgrade to this version. Additionally, client libraries have been updated to reject policies containing the a: fragment on affected app versions: ledger-bitcoin Python client v0.2.1, JavaScript client v0.2.1, and Rust crate v0.1.3 [1]. Software wallets are recommended to implement on-screen address verification to catch discrepancies [1]. The vulnerability is not listed in CISA KEV as of the publication date.