# 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.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Mar 2026
- **Updated:** 7 Aug 2026
- **Also known as:** GHSA-2w8x-224x-785m

## 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.

Weakness: CWE-325 (Missing Cryptographic Step), CWE-347 (Improper Verification of Cryptographic Signature)

## Which versions are affected by CVE-2026-4258?

2 open source packages ship an affected version, including sjcl. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `sjcl` | npm | All versions | 1.0.9 |
| `sjcl` | npm | All versions | 1.0.9 |

Products: 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-4258 and fix it if it is affected.

What it is: 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.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-4258 exists.

Affected packages and fixed versions:
- sjcl (npm): affected all versions; fixed in 1.0.9
- sjcl (npm): affected all versions; fixed in 1.0.9

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-4258/ (Markdown: https://insights.sbomify.com/CVE-2026-4258/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-4258
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-4258
- OSV: https://osv.dev/vulnerability/CVE-2026-4258

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-4258/
Summaries are generated and may contain mistakes; the official description above is the record.