---
id: CVE-2026-55174
title: >-
  UltrafastSecp256k1 is a high-performance, multi-backend secp256k1 engine with
  reproducible audit evidence, compatibility shims, and profile-based review
  scopes
summary: >-
  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 ver…
severity: medium
cvss: 5.9
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N'
cwe:
  - CWE-345
  - CWE-347
vendor: shrec
product: UltrafastSecp256k1
affected:
  - UltrafastSecp256k1 < 4.2.0
published: '2026-09-30'
updated: '2026-09-30'
sourceUpdated: '2026-09-30T20:17:33.243'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-55174'
references:
  - url: >-
      https://github.com/shrec/UltrafastSecp256k1/commit/5478ef566c6af91b48a45c0c61f161f5b1071981
    label: security-advisories@github.com
  - url: 'https://github.com/shrec/UltrafastSecp256k1/releases/tag/v4.2.0'
    label: security-advisories@github.com
  - url: 'https://github.com/shrec/UltrafastSecp256k1/releases/tag/v4.2.1'
    label: security-advisories@github.com
  - url: >-
      https://github.com/shrec/UltrafastSecp256k1/security/advisories/GHSA-c7q2-gv3g-rgxm
    label: security-advisories@github.com
  - url: >-
      https://github.com/shrec/UltrafastSecp256k1/security/advisories/GHSA-c7q2-gv3g-rgxm
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
  - cve.org
  - exploit-available
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-30T19:51:52.522461Z'
ingestedAt: '2026-09-30T16:10:07.653Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.