# CVE-2026-4599: jsrsasign: Incomplete Comparison Allows DSA Private Key Recovery via Biased Nonce Generation

> An attacker can recover private keys by exploiting biased DSA nonces caused by incorrect comparison logic in the jsrsasign library.

- **Severity:** Critical 9.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 23 Mar 2026
- **Updated:** 10 Sep 2026
- **Also known as:** GHSA-5jx8-q4cp-rhh6

## What is CVE-2026-4599?

CVE-2026-4599 is a critical vulnerability in jsrsasign, published on 23 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 jsrsasign from 7.0.0 and before 11.1.1 are vulnerable to Incomplete Comparison with Missing Factors via the getRandomBigIntegerZeroToMax and getRandomBigIntegerMinToMax functions in src/crypto-1.1.js; an attacker can recover the private key by exploiting the incorrect compareTo checks that accept out-of-range candidates and thus bias DSA nonces during signature generation.

Weakness: CWE-338 (Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)), CWE-1023 (Incomplete Comparison with Missing Factors)

## Which versions are affected by CVE-2026-4599?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `jsrsasign` | npm | From 7.0.0 | 11.1.1 |
| `jsrsasign` | npm | From 7.0.0 | 11.1.1 |

Products: Kjur Jsrsasign.

## How do I fix CVE-2026-4599?

Upgrade jsrsasign to 11.1.1 or later.

## Is CVE-2026-4599 being exploited?

There is no known exploitation of CVE-2026-4599 in the wild and no public exploit code.

## Other vulnerabilities in jsrsasign

- [CVE-2020-14967](https://insights.sbomify.com/CVE-2020-14967/): RSA PKCS#1 decryption vulnerability with prepending zeros in jsrsasign (critical 9.8)
- [CVE-2020-14968](https://insights.sbomify.com/CVE-2020-14968/): RSA-PSS signature validation vulnerability by prepending zeros in jsrsasign (critical 9.8)
- [CVE-2026-4601](https://insights.sbomify.com/CVE-2026-4601/): jsrsasign: Missing cryptographic validation during DSA signing enables private key extraction (critical 9.4)
- [CVE-2026-4600](https://insights.sbomify.com/CVE-2026-4600/): jsrsasign: DSA signatures or X.509 certificates can be forged via DSA domain-parameter validation in KJUR.crypto.DSA.setPublic (critical 9.1)
- [CVE-2021-30246](https://insights.sbomify.com/CVE-2021-30246/): RSA signature validation vulnerability on maleable encoded message in jsrsasign (critical 9.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-4599 and fix it if it is affected.

What it is: CVE-2026-4599 is a critical vulnerability in jsrsasign, published on 23 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-4599 in the wild and no public exploit code.

Affected packages and fixed versions:
- jsrsasign (npm): affected from 7.0.0; fixed in 11.1.1
- jsrsasign (npm): affected from 7.0.0; fixed in 11.1.1

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-2026-4599/ (Markdown: https://insights.sbomify.com/CVE-2026-4599/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-4599
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-4599
- OSV: https://osv.dev/vulnerability/CVE-2026-4599

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-4599/
Summaries are generated and may contain mistakes; the official description above is the record.