CVE-2026-4599: jsrsasign (npm)

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
EPSS 0.8%, percentile 56: FIRST’s model estimates a 0.8% chance of exploitation activity in the next 30 days, higher than 56% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
Only applies if your dependency tree includes jsrsasign (npm) >= 7.0.0, < 11.1.1, fixed in 11.1.1. Check your lockfile, including transitive dependencies.

What it is

Versions of the package jsrsasign from 7.0.0 and before 11.1.1 are vulnerable to Incomplete Comparison with Missing Factors via the getRandomBigIntegerZeroToMax and getRandomBigIntegerMinToMax functions in src/crypto-1.1.js; an attacker can recover the private key by exploiting the incorrect compareTo checks that accept out-of-range candidates and thus bias DSA nonces during signature generation.

From the GitHub advisory

Weakness type: CWE-1023, CWE-338.

Product: jsrsasign (npm) · Assigned by: snyk · Published: 2026-03-23

Affected and fixed versions

Ecosystem	Package	Vulnerable	First fixed
npm	`jsrsasign`	>= 7.0.0, < 11.1.1	11.1.1

Vendor	Product	Affected versions (per CVE record)
n/a	jsrsasign	7.0.0 < 11.1.1
n/a	org.webjars.npm:jsrsasign	8.0.12 < *

Severity scores

Scored by	CVSS	Score	Vector
snyk	4.0	9.3 Critical	`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`
snyk	3.1	9.1 Critical	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`
redhat-SADP	3.1	9.1 Critical	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`
GitHub	4.0	9.3	`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`

Attack vector: network (remotely reachable)
Attack complexity: low
Attack requirements: none
Privileges required: none (no login)
User interaction: none

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
CISA SSVC assessment: exploitation none, automatable yes, technical impact total.
FIRST EPSS (model of 2026-10-21): 0.81% probability of exploitation activity in the next 30 days; percentile 56.

Timeline

2026-03-23 — CVE record published by snyk
2026-03-23 — GitHub-reviewed advisory GHSA-5jx8-q4cp-rhh6 published (critical)
2026-09-10 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

access.redhat.com access.redhat.com
access.redhat.com access.redhat.com
access.redhat.com access.redhat.com
access.redhat.com access.redhat.com
access.redhat.com access.redhat.com
access.redhat.com access.redhat.com
access.redhat.com access.redhat.com

Vulnerability records

GitHub Advisory GHSA-5jx8-q4cp-rhh6 github.com
CVE.org record CVE-2026-4599 cve.org
NVD entry CVE-2026-4599 nvd.nist.gov

Other references from the CVE record and advisory

security.snyk.io security.snyk.io
security.snyk.io security.snyk.io
gist.github.com gist.github.com
github.com github.com
github.com github.com
access.redhat.com access.redhat.com
RHBZ#2450207 bugzilla.redhat.com
security.access.redhat.com security.access.redhat.com

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