Vulnerability in Bitwiseshiftleft Stanford JavaScript Crypto Library
CVE-2026-4258
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
EPSS exploit prediction
EPSS: 0.004 (27.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 28th percentile — 27.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.004 · change: +0.001
Affected products
- Bitwiseshiftleft Stanford JavaScript Crypto Library
- Org.webjars.npm:sjcl — versions 0
- Sjcl — versions 0
Weakness classification (CWE)
References
- security.snyk.io/vuln/SNYK-JS-SJCL-15369617 (Exploit, Third Party Advisory)
- gist.github.com/Kr0emer/2560f98edb10b0b34f2438cd63913c47 (Exploit, Third Party Advisory, Mitigation)
- github.com/bitwiseshiftleft/sjcl/blob/master/core/ecc.js#L454-L461 (Broken Link)
- github.com/bitwiseshiftleft/sjcl/commit/ee307459972442a17beebc29dc331fffd8aff796 (Patch)
- security.snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-15751243
Frequently asked questions
- What is CVE-2026-4258?
- CVE-2026-4258 is a high-severity vulnerability in Bitwiseshiftleft Stanford JavaScript Crypto Library, classified under Improper Verification of Cryptographic Signature. CVSS score: 7.5/10. Published 2026-03-17.
- How severe is CVE-2026-4258?
- High severity. CVSS v3 base score is 7.5 out of 10.