CVE-2026-4258: All versions of the package sjcl are vulnerable to Improper Verification of Cryptographic Signature due to missing point-on-curve validation in sjcl

All versions of the package sjcl are vulnerable to Improper Verification of Cryptographic Signature due to missing point-on-curve validation in sjcl.ecc.basicKey.publicKey(). An attacker can recover a victim's ECDH private key by sending crafted off-curve public keys and observing ECDH outputs. The dhJavaEc() function directly returns the raw x-coordinate of the scalar multiplication result (no hashing), providing a plaintext oracle without requiring any decryption feedback.