CVE-2026-55174: Shrec ULTRAFASTSECP256K1

Medium severity, CVSS 5.9. EPSS: 0.2% chance of exploitation in the next 30 days.

UltrafastSecp256k1 is a high-performance, multi-backend secp256k1 engine with reproducible audit evidence, compatibility shims, and profile-based review scopes. Prior to version 4.2.0, UltrafastSecp256k1's ECDSA adaptor pre-signature verification accepts forged adaptor pre-signatures whose "r" value is not cryptographically bound to the adaptor point "T". This issue has been patched in version 4.2.0.

Affected products

• Shrec ULTRAFASTSECP256K1: before 4.2.0 (fixed in 4.2.0)

Published 2026-09-30. Last modified 2026-09-30.