CVE-2026-4603: jsrsasign Division By Zero Allows Invalid Vulnerability

LOW
Advisory Identifier: GHSA-464q-cqxq-xhgr
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CVSS 5.9
CWE-369
Published
Advisory Summary

CVE-2026-4603 is a LOW (CVSS 5.9) division by zero allows invalid vulnerability (CWE-369: Divide By Zero) affecting jsrsasign libraries in the npm ecosystem. The issue involves division by zero allows invalid jwk modulus to cause deterministic zero output in rsa operations. Remediation is available by upgrading affected packages to version 11.1.1.

CVE-2026-4603 at a Glance

CVE Identifier CVE-2026-4603
GHSA Identifier GHSA-464q-cqxq-xhgr
Severity LOW
CVSS v3.1 Base Score 5.9
CWE Classification CWE-369: Divide By Zero
Affected Product jsrsasign
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 5.9

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L).

Attack Vector Local (AV:L)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability Low (A:L)

How to Fix CVE-2026-4603

To remediate this vulnerability, upgrade all affected jsrsasign dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

jsrsasign fixed: 11.1.1 
npm install jsrsasign@11.1.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls jsrsasign

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-4603, inspect your project dependencies using npm:

npm ls jsrsasign

Analyze the terminal output to locate any version of jsrsasign in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 11.1.1), your application is affected.

Note: The npm ls jsrsasign command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-369: Divide By Zero, where the product divides a value by zero. In jsrsasign, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

Versions of the package jsrsasign before 11.1.1 are vulnerable to Division by zero due to the RSASetPublic/KEYUTIL parsing path in ext/rsa.js and the BigInteger.modPowInt reduction logic in ext/jsbn.js. An attacker can force RSA public-key operations (e.g., verify and encryption) to collapse to deterministic zero outputs and hide “invalid key” errors by supplying a JWK whose modulus decodes to zero.

CVE-2026-4603 Affected jsrsasign Versions

1 component(s)
Fixed Versions:
11.1.1
Product / Package Ecosystem Affected Versions Fixed Version
jsrsasign
npm/jsrsasign
npm
< 11.1.1
11.1.1

References

NVD — CVE-2026-4603 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-4603
jsrsasign Source Repository REPOSITORY
https://github.com/kjur/jsrsasign/pull/649
Security Fix Commit FIX COMMIT
https://github.com/kjur/jsrsasign/commit/dc41d49fac4297e7a737a3ef8ebd0aa9c49ef93f
jsrsasign Source Repository REPOSITORY
https://gist.github.com/Kr0emer/5366b7364c4fbf7e754bc377f321e9f3
jsrsasign Source Repository REPOSITORY
https://github.com/kjur/jsrsasign
jsrsasign Security Information SECURITY
https://security.snyk.io/vuln/SNYK-JS-JSRSASIGN-15371176

Frequently Asked Questions

What is CVE-2026-4603?
CVE-2026-4603 is a security vulnerability in jsrsasign involving Division by Zero Allows Invalid JWK Modulus to Cause Deterministic Zero Output in RSA Operations under CWE-369: Divide By Zero.
Which jsrsasign versions are affected?
Affected versions include releases prior to 11.1.1 across affected packages: jsrsasign.
What version fixes CVE-2026-4603?
Upgrading to 11.1.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is jsrsasign affected?
Yes, jsrsasign is affected in releases prior to 11.1.1. Upgrade your dependency to 11.1.1 or later.
What is the CVSS score of CVE-2026-4603?
CVE-2026-4603 has a CVSS v3.1 base score of 5.9 (LOW) with vector string CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L.
What CWE is associated with CVE-2026-4603?
CVE-2026-4603 is classified under CWE-369: Divide By Zero (The product divides a value by zero.).
How can I check npm dependencies for CVE-2026-4603?
Run the dependency tree command: 'npm ls jsrsasign'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-464q-cqxq-xhgr",
  "modified" : "2026-03-30T19:30:16Z",
  "published" : "2026-03-23T06:30:29Z",
  "aliases" : [ "CVE-2026-4603" ],
  "summary" : "jsrsasign: Division by Zero Allows Invalid JWK Modulus to Cause Deterministic Zero Output in RSA Operations",
  "details" : "Versions of the package jsrsasign before 11.1.1 are vulnerable to Division by zero due to the RSASetPublic/KEYUTIL parsing path in ext/rsa.js and the BigInteger.modPowInt reduction logic in ext/jsbn.js. An attacker can force RSA public-key operations (e.g., verify and encryption) to collapse to deterministic zero outputs and hide “invalid key” errors by supplying a JWK whose modulus decodes to zero.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "jsrsasign"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "11.1.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-4603"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/kjur/jsrsasign/pull/649"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/kjur/jsrsasign/commit/dc41d49fac4297e7a737a3ef8ebd0aa9c49ef93f"
  }, {
    "type" : "WEB",
    "url" : "https://gist.github.com/Kr0emer/5366b7364c4fbf7e754bc377f321e9f3"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/kjur/jsrsasign"
  }, {
    "type" : "WEB",
    "url" : "https://security.snyk.io/vuln/SNYK-JS-JSRSASIGN-15371176"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-369" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-30T19:30:16Z",
    "nvd_published_at" : "2026-03-23T06:16:22Z"
  }
}