CVE-2026-55174
Received Received - Intake

ECDSA Adaptor Signature Forgery in UltrafastSecp256k1

Publication date: 2026-09-30

Last updated on: 2026-09-30

Assigner: GitHub, Inc.

Description
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.

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Meta Information

Published
2026-09-30
Last Modified
2026-09-30
Generated
2026-09-30
AI Q&A
2026-09-30
EPSS Evaluated
N/A
NVD
CVE-2026-55174
EUVD
EUVD-2026-90188

Affected Vendors & Products

Showing 3 associated CPEs
Vendor Product Version / Range
ultrafastsecp256k1 ultrafastsecp256k1 4.2.0
shrec ultrafastsecp256k1 4.2.0
shrec ultrafastsecp256k1 4.2.1

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-345 The product does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data.
CWE-347 The product does not verify, or incorrectly verifies, the cryptographic signature for data.

Attack-Flow Graph

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Executive Summary

UltrafastSecp256k1 before version 4.2.0 has a flaw in its ECDSA adaptor pre-signature verification. It accepts forged adaptor pre-signatures where the 'r' value is not properly cryptographically linked to the adaptor point 'T'. This could allow an attacker to manipulate pre-signatures without detection.

Detection Guidance

Detection requires checking the installed version of UltrafastSecp256k1. Use commands like 'pkg-config --modversion ultrafastsecp256k1' or inspect build files for version 4.2.0 or earlier. If vulnerable, upgrade to 4.2.1 or later.

Impact Analysis

This vulnerability could allow attackers to forge valid adaptor pre-signatures, potentially enabling unauthorized transactions or compromising cryptographic operations that rely on UltrafastSecp256k1's ECDSA adaptor signatures. Systems using affected versions may face security breaches or financial losses.

Compliance Impact

The vulnerability allows forged adaptor pre-signatures that pass verification but cannot be adapted into valid ECDSA signatures, breaking cryptographic guarantees. This could undermine integrity in systems handling sensitive data, potentially violating GDPR's integrity principle or HIPAA's security requirements for data protection and integrity.

Mitigation Strategies

Update UltrafastSecp256k1 to version 4.2.0 or later to patch the vulnerability. The issue involves forged adaptor pre-signatures in ECDSA operations, so applying the latest version resolves the flaw.

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