CVE-2026-4603
jsrsasign: Division by Zero Allows Invalid JWK Modulus to Cause Deterministic Zero Output in RSA Operations
5.9
MEDIUM
CVSS 3.1
EPSS 0.01%
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.
How to fix CVE-2026-4603
To remediate CVE-2026-4603, upgrade the affected package to a fixed version below.
- —upgrade to 11.1.1 or later
Is CVE-2026-4603 being exploited?
Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- from 0, < 11.1.1
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 4.0 | — | 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 |
| osv | CVSS 3.1 | MEDIUM5.9 | CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L |