CVE-2026-4601: Private Key Recovery in jsrsasign

The core of this vulnerability lies in the DSA signing implementation within jsrsasign. An attacker can craft malicious input that forces the r or s values in the signature to be zero. This triggers the library to emit an invalid signature without attempting a retry. By analyzing this invalid signature, an attacker can mathematically solve for the private key x. The compromise of the private key grants the attacker the ability to impersonate legitimate users, decrypt sensitive communications, and forge digital signatures, effectively undermining the security of any application relying on jsrsasign for DSA-based cryptography. This is particularly concerning for applications handling financial transactions, authentication tokens, or any data requiring strong cryptographic protection.

1. Reserved2026-03-22
2. Published2026-03-23
3. Modified2026-03-29
4. EPSS updated2026-03-30

The primary mitigation for CVE-2026-4601 is to immediately upgrade to jsrsasign version 11.1.1 or later. This version contains a fix that prevents the private key recovery vulnerability. If upgrading is not immediately feasible due to compatibility issues or deployment constraints, consider implementing input validation on DSA signatures to reject signatures with r or s values of zero. While this is not a complete solution, it can provide a temporary layer of defense. Monitor your applications for unusual signature generation patterns that might indicate an attempted exploitation. After upgrading, verify the fix by attempting to generate a DSA signature with a manipulated r or s value; the library should now reject the signature and not emit an invalid result.