CVE-2026-4602: jsrsasign Vulnerability Leading to Signature Verification Bypass
Summary
CVE-2026-4602: jsrsasign: Negative Exponent Handling Leads to Signature Verification Bypass. 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 functionalities, including digital signatures and key management. It is commonly utilized in web applications to ensure secure communications and data integrity. However, certain versions of jsrsasign are vulnerable to a significant flaw that can compromise the security of applications relying on this library.
Vulnerability Detail
The vulnerability arises from incorrect handling of negative exponents in the ext/jsbn2.js file within the jsrsasign package. Specifically, versions prior to 11.1.1 allow an attacker to manipulate the computation of modular inverses by invoking the modPow function with a negative exponent. This can lead to a bypass of signature verification, potentially allowing unauthorized access or manipulation of sensitive data. The flaw is categorized under CWE-681, indicating an incorrect conversion between numeric types, which can have severe implications for the integrity of cryptographic operations.
How To Fix
Minimum fixed version
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
If immediate upgrading is not feasible, consider implementing additional validation checks on the inputs to the modPow function to prevent negative exponents from being processed. However, this is not a complete fix and should only be a temporary measure until the package can be updated.
Conclusion
The jsrsasign vulnerability (CVE-2026-4602) presents a significant risk due to improper handling of negative exponents, which can lead to a bypass of signature verification. It is crucial for developers to update to version 11.1.1 or later to mitigate this risk and ensure the integrity of their applications.
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FAQ
The CVSS score of this vulnerability is 7.5, indicating a high severity level.
Versions of jsrsasign prior to 11.1.1 are affected by this vulnerability.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without requiring any signup.
Exploitation of this vulnerability can lead to unauthorized access and manipulation of data, as it allows attackers to bypass signature verification.
Yes, Vulert can monitor and alert you in real-time for open-source vulnerabilities in your software using just the package-lock.json file.
References
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