The vulnerability in digitalbazaar's forge (node-forge) library affects Ed25519 signature verification prior to version 1.4.0. The verification process improperly accepts non-canonical signatures where the scalar S is not reduced modulo the group order (S >= L). This means that both a valid signature and a forged variant (S + L) verify successfully, whereas the Node.js crypto.verify method (OpenSSL-backed) correctly rejects the forged variant. This signature malleability can be exploited to bypass authentication and authorization mechanisms that rely on signature uniqueness, such as deduplication by signature bytes, replay tracking, or signed-object canonicalization checks. The vulnerability is tracked as CVE-2026-33895 with a CVSS 3.1 score of 7.5 (high severity). The issue is patched in forge version 1.4.0. Red Hat advisories confirm the vulnerability and provide updates for affected products.

This vulnerability allows attackers to forge Ed25519 signatures by exploiting signature malleability, potentially bypassing authentication and authorization controls in applications that depend on signature uniqueness. While it does not directly compromise confidentiality or availability, it impacts integrity and trust in cryptographic verification, which can lead to unauthorized actions or access.

A fix is available in forge version 1.4.0. Users and organizations should upgrade to version 1.4.0 or later to remediate this vulnerability. Red Hat has issued advisories and updates addressing this issue in their affected products. Applying these vendor-provided patches is the recommended remediation. No additional mitigations are specified by the vendor advisory.