CVE-2026-4258: Bitwiseshiftleft Stanford JavaScript Crypto Library

High severity, CVSS 7.5. EPSS: 0.3% chance of exploitation in the next 30 days.

Versions of the package sjcl before 1.0.9 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.

Affected products

• Bitwiseshiftleft Stanford JavaScript Crypto Library: up to and including 1.0.8

Published 2026-03-17. Last modified 2026-07-28.