[Lightning-dev] CVE-2020-26895: LND Low-S Tx-Relay Standardness

[neocarmack]

Background

CVE-2020-26895 was fully disclosed on Oct 20, 2020.

LND v0.10.0-beta, released on April 29,2020, fixed this vulnerability.

Description of vulnerability

High S signature causes signature malleability related to ECDSA signature encoding . To fix signature malleability, Low S signature is propsed in BIP-0146, and high s signature are no longer accepted by btccore.

Affected Component

OBD core, client sdk

Platform

All

Proof-of-concept

CVE-2020-26895 fully disclosed this vunerability.

Vulnerability reproduction output

N/A

Fix

To OBD node, If a signature from client passing to ECDSA verification does not pass the Low S value check and is not an empty byte array, the entire script evaluates to false immediately. OBD shall reject this signature.

Reference

BIP-0146
CVE-2020-26895
Low S signature to fix