CVE-2026-4601: jsrsasign Vulnerability Allows Private Key Extraction via DSA Signing
Summary
CVE-2026-4601: jsrsasign: Missing cryptographic validation during DSA signing enables private key extraction. Affects jsrsasign versions < 11.1.1. Fixed in 11.1.1. How to fix ↓
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Background
jsrsasign is a widely used JavaScript library that provides cryptographic functions, including digital signatures, encryption, and key management. It is commonly utilized in web applications to secure communications and authenticate users. The library's DSA signing implementation has a critical vulnerability that can lead to the exposure of private keys, compromising the security of applications that rely on it.
Vulnerability Detail
The vulnerability arises from a missing cryptographic validation step in the DSA signing process of the jsrsasign library. Specifically, when the KJUR.crypto.DSA.signWithMessageHash function is called, an attacker can manipulate the signing process by forcing the signature components 'r' or 's' to be zero. This results in the generation of an invalid signature without any retry mechanism, allowing the attacker to solve for the private key 'x' from the resulting signature. The ramifications of this vulnerability are severe, as it can lead to unauthorized access and control over systems that depend on the compromised private keys.
How To Fix
Latest published version: 11.1.5 as of 23 Oct 2026
npm install jsrsasign@11.1.5Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
11.1.1
This is the first release that contains the fix.
npm install jsrsasign@11.1.1Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, consider implementing additional validation checks in your application to ensure that the signature components 'r' and 's' are not zero before proceeding with any cryptographic operations. However, this is not a substitute for updating the library.
Conclusion
The jsrsasign library has a critical vulnerability that allows for private key extraction due to missing cryptographic validation during DSA signing. It is crucial for developers using this library to update to version 11.1.1 or later to mitigate the risk. Additionally, implementing workarounds can provide temporary relief, but updating the library is the most effective solution.
See every vulnerability recorded for jsrsasign →
FAQ
The CVSS score of this vulnerability is 8.7, indicating a high severity level.
Versions of jsrsasign prior to 11.1.1 are vulnerable to this issue.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without needing to sign up.
If exploited, this vulnerability can lead to the extraction of private keys, resulting in unauthorized access to sensitive data and systems.
Yes, Vulert can monitor your project for open-source vulnerabilities in real-time using just the package-lock.json file.
References
Related vulnerabilities
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