CVE-2026-4602

jsrsasign: Negative Exponent Handling Leads to Signature Verification Bypass

8.7 HighFix available

Versions of the package jsrsasign before 11.1.1 are vulnerable to Incorrect Conversion between Numeric Types due to handling negative exponents in ext/jsbn2.js. An attacker can force the computation of incorrect modular inverses and break signature verification by calling modPow with a negative exponent.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: None
Availability: High

Exploit likelihood

0.50%Up 0.5 points since Mar 23, 2026

What each source reports

CVE List Score used 8.7

Record: CVE-2026-4602
CVSS 4.0: 8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness: CWE-681, CWE-681
Updated: 2026-11-02

EUVDEUVD-2026-14379 8.7

Record: EUVD-2026-14379
CVSS 4.0: 8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P
Updated: 2026-11-02

GitHub AdvisoriesGHSA-8qwj-4jxw-m8jw 7.7

jsrsasign: Negative Exponent Handling Leads to Signature Verification Bypass

Record: GHSA-8qwj-4jxw-m8jw
CVSS 4.0: 7.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-681
Updated: 2026-11-02

NVD 7.7

Record: CVE-2026-4602
CVSS 4.0: 7.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness: CWE-681
Updated: 2026-11-02

OSV 7.7

Record: CVE-2026-4602
CVSS 4.0: 7.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P
Weakness: CWE-681
Updated: 2026-11-02

OSVGHSA-8qwj-4jxw-m8jw 7.7

jsrsasign: Negative Exponent Handling Leads to Signature Verification Bypass

Record: GHSA-8qwj-4jxw-m8jw
CVSS 4.0: 7.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-681
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`jsrsasign` npm	before 11.1.1	11.1.1

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-4602 is a high vulnerability (CVSS 8.7) in Kjur Jsrsasign, published March 23, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.50%, the 42nd percentile. Fixed in jsrsasign 11.1.1.

References

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