CVE-2026-4603: Versions of the package jsrsasign before 11.1.1 are vulnerable to Division by zero due to the RSASetPublic/KEY

Routine

MEDIUM 5.9UPGRADE

CVE-2026-4603 is a medium-severity flaw (CVSS 5.9) affecting jsrsasign. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	5.9 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.1% (top 99%)
CISA exploited list	No
Weakness	CWE-369
Published	2026-03-23
Last modified	2026-06-22

Publisher (CNA): Snyk · Vendor: kjur

Last updated 2026-06-22 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-23 06:16 UTCPublished CVE record published
2026-06-22 03:18 UTCUpdated Record last modified

kjur jsrsasign UPGRADE

Affected: < 11.1.1

Fixed in: 11.1.1

Safe to downgrade to: no unaffected older release

1. Check installed version

npm ls jsrsasign

2. UPGRADE to 11.1.1

npm install jsrsasign@">=11.1.1"

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-4603?

jsrsasign: upgrade to 11.1.1. Exact commands for each OS are on this page.

Is CVE-2026-4603 being exploited?

CVE-2026-4603 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-4603 affect?

CVE-2026-4603 affects jsrsasign. Severity is medium (CVSS 5.9). 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

How urgent is CVE-2026-4603?

Priority 26/100. Public exploit reference

Related CVEs

CVE-2026-4602 HIGH 7.5 UPGRADE Versions of the package jsrsasign before 11.1.1 are vulnerable to Incorrect Conversion between Numeric Types d
CVE-2026-4601 HIGH 8.7 UPGRADE Versions of the package jsrsasign before 11.1.1 are vulnerable to Missing Cryptographic Step via the KJUR.cryp
CVE-2026-4600 HIGH 7.4 UPGRADE Versions of the package jsrsasign before 11.1.1 are vulnerable to Improper Verification of Cryptographic Signa
CVE-2026-4599 CRITICAL 9.1 UPGRADE Versions of the package jsrsasign from 7.0.0 and before 11.1.1 are vulnerable to Incomplete Comparison with Mi
CVE-2026-4598 HIGH 7.5 UPGRADE Versions of the package jsrsasign before 11.1.1 are vulnerable to Infinite loop via the bnModInverse function

References

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