5.3

CVE-2026-4603: kjur jsrsasign Divide By Zero

CVSS: 5.3v3.1MediumAnalyzed
AliasesGHSA-464q-cqxq-xhgr
Published 23-03-2026Last modified 23-03-2026
Open JSON

Vulnerability summary

CVE-2026-4603 is a medium (CVSS 5.3) Divide By Zero vulnerability in kjur jsrsasign. EPSS estimates a 0.11% chance of exploitation in the next 30 days, higher than 1.4% of scored vulnerabilities. 1 public exploit is recorded.

Overall risk
31/100
0100
Medium · default modelHow is this calculated?
CVSS score
5.3/10
010
Medium · v3.1 (NVD)
EPSS score
0.11%
0%100%
Low · +0.01 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits1github

Timeline

  1. 23-03-2026
    PublishedVulnerability first disclosed.
  2. 23-03-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

5 scores · 3 sources · 2 versions

EPSS trend

Probability

0.11%

Chance of exploitation in the next 30 days

Percentile

1%

Versus all other CVEs

30-day change

+0.01 pp

From 0.10% on 21-09-2026

21-09-202621-10-2026
EPSS score
0.11%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

1 found
  • githubUnverified

    5366B7364C4Fbf7E754Bc377F321E9F3

    Maturity: poc

Weaknesses

CWE · root cause

Affected systems

Kjur1 product
Npm1 product
  • jsrsasign< 11.1.1

2 vendors · 2 products

References

6 links