Vulnerability · Published Sep 30, 2026 · Assigned by GitHub_M

CVE-2026-55174UltrafastSecp256k1: ECDSA adaptor verification accepts non-adaptable pre-signatures due to missing DLEQ binding

Medium 5.9

In plain English

A medium-severity insufficient verification of data authenticity in UltrafastSecp256k1 from shrec. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 4% of all known vulnerabilities).

Severity (CVSS 3.1)5.9Medium

Exploit odds (30 days)0.1%top 95.8% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
shrec	UltrafastSecp256k1	< 4.2.0

Weakness: CWE-345, CWE-347 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

References

https://github.com/shrec/UltrafastSecp256k1/security/advisories/GHSA-c7q2-gv3g-rgxm x_refsource_CONFIRM
https://github.com/shrec/UltrafastSecp256k1/commit/5478ef566c6af91b48a45c0c61f161f5b1071981 x_refsource_MISC
https://github.com/shrec/UltrafastSecp256k1/releases/tag/v4.2.0 x_refsource_MISC
https://github.com/shrec/UltrafastSecp256k1/releases/tag/v4.2.1 x_refsource_MISC