CVE-2026-4258 sjcl is 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 due to missing point-on-curve validation in the sjcl library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-4258?
CVE-2026-4258 is a high-severity vulnerability in org.webjars.npm:sjcl, published on 17 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2026-4258?
2 open source packages ship an affected version, including sjcl. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
sjcl npm | All versions | 1.0.9 |
sjcl npm | All versions | 1.0.9 |
Products include Bitwiseshiftleft Stanford Javascript Crypto Library.
How do I fix CVE-2026-4258?
Upgrade sjcl to 1.0.9 or later.
Is CVE-2026-4258 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-4258 exists.
Sources
Also known as GHSA-2w8x-224x-785m.