CVE-2026-4600: DSA Signature Forgery in jsrsasign

The core of this vulnerability lies in the KJUR.crypto.DSA.setPublic function and related DSA/X509 verification flows within src/dsa-2.0.js. The validation of domain parameters (g, y, and r) is insufficient, allowing an attacker to craft malicious parameters (e.g., g=1, y=1, r=1) that satisfy the verification equation regardless of the underlying hash. This effectively bypasses the signature verification process. An attacker could leverage this to forge digital signatures, potentially impersonating legitimate entities or injecting malicious code into applications that rely on jsrsasign for authentication or integrity checks. The impact is particularly severe in applications using jsrsasign for secure communication or data validation, as it could lead to complete compromise of the system’s trust model. This vulnerability shares similarities with other cryptographic signature forgery vulnerabilities where inadequate parameter validation is exploited.

1. Reserved2026-03-22
2. Published2026-03-23
3. Modified2026-03-30
4. EPSS updated2026-03-30

The primary mitigation for CVE-2026-4600 is to upgrade to jsrsasign version 11.1.1 or later, which includes the necessary fixes for domain parameter validation. If upgrading immediately is not feasible, consider implementing temporary workarounds. While a direct WAF rule is unlikely to be effective due to the nature of the cryptographic flaw, strict input validation on any data processed by jsrsasign can help reduce the attack surface. Carefully review all code that utilizes KJUR.crypto.DSA.setPublic and ensure that domain parameters are obtained from trusted sources and thoroughly validated before use. Monitor application logs for any unusual signature verification errors or attempts to use suspicious domain parameters. After upgrading, confirm the fix by attempting to generate and verify signatures with known malicious domain parameters – they should be rejected.