CVE-2026-4258

Description

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.

How to fix CVE-2026-4258

To remediate CVE-2026-4258, upgrade the affected package to a fixed version below.

• —upgrade to 1.0.9 or later

Is CVE-2026-4258 being exploited?

Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.

Affected packages (1)

• from 0, < 1.0.9

CVSS scores

References (6)

• ADVISORYnvd.nist.gov/vuln/detail/CVE-2026-4258
• PATCHgithub.com/bitwiseshiftleft/sjcl
• WEBgist.github.com/Kr0emer/2560f98edb10b0b34f2438cd63913c47
• WEBgithub.com/bitwiseshiftleft/sjcl/blob/master/core/ecc.js#L454-L461