What’s Vulnerable › Vulnerabilities

CVE-2026-4603

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-03-23 · updated 2026-06-22
• Weakness: CWE-369

Description

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.

Affected products

• jsrsasign: before 11.1.1 — fixed in 11.1.1

How to fix

Upgrade to a fixed version: jsrsasign 11.1.1. Check the vendor advisory for mitigations.

References

• https://gist.github.com/Kr0emer/5366b7364c4fbf7e754bc377f321e9f3
• https://github.com/kjur/jsrsasign/commit/dc41d49fac4297e7a737a3ef8ebd0aa9c49ef93f
• https://github.com/kjur/jsrsasign/pull/649
• https://security.snyk.io/vuln/SNYK-JS-JSRSASIGN-15371176

Get alerted when CVE-2026-4603 or the next vulnerability affects your stack