CVE-2026-4602 — Versions of the package jsrsasign before 11.1.1 are vulnerable to Incorrect Conversion…
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.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 0.9% (30-day exploitation probability)+9
- Technical severity (high)+6
- CISA SSVC: exploitation "poc"+5
- Automatable exploitation (SSVC)+3
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
- Documented mitigation — gist.github.com (NIST National Vulnerability Database)
- Documented patch — github.com (NIST National Vulnerability Database)
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Kjur Jsrsasign).
- The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
- Apply the fixed version or the patch documented under Remediation.
- Search available logs for exploit probes, errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 8.7 | CVSS 4.0 | High | — | — | snyk via CVE Program (cve.org) e CISA ADP |
| 7.7 | CVSS 4.0 | High | — | — | report@snyk.io via NIST National Vulnerability Database |
| 7.5 | CVSS 3.1 | High | 3.9 | 3.6 | report@snyk.io via NIST National Vulnerability Database |
| 7.5 | CVSS 3.1 | High | 3.9 | 3.6 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c via NIST National Vulnerability Database |
| 7.5 | CVSS 3.1 | High | — | — | snyk via CVE Program (cve.org) e CISA ADP |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (score shown at the top: report@snyk.io) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
EPSS over time FIRST
Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.88%
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Timeline
What happened to this CVE, newest first.
- 2026
- SSVC assessment updated
- Record published
- Fix documented
- CVSS changed · 7.5
- Source status changed · → Modified
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× Official description updated · Oct 13, 2026 – Oct 13, 2026
References
15 on the record
- github.com/kjur/jsrsasign/commit/5ea1c32bb2aa894b4bd29849839afe4f98728195
- gist.github.com/Kr0emer/7ecd2be7d17419e4677315ef3758faf5
- security.snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-15812274
- access.redhat.com/errata/RHSA-2026:19409
- access.redhat.com/errata/RHSA-2026:6926
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4602.json
- bugzilla.redhat.com/show_bug.cgi
- access.redhat.com/errata/RHSA-2026:19410
- access.redhat.com/errata/RHSA-2026:19375
- access.redhat.com/errata/RHSA-2026:6568
- access.redhat.com/errata/RHSA-2026:6912
- github.com/kjur/jsrsasign/pull/650
- access.redhat.com/security/cve/CVE-2026-4602
- access.redhat.com/errata/RHSA-2026:6720
- security.snyk.io/vuln/SNYK-JS-JSRSASIGN-15371175
Elsewhere on this site
Related CVEs (same products)
- Medium CVE-2026-4603 Versions of the package jsrsasign before 11.1.1 are vulnerable to Division by zero due… Mar 23, 2026
- High CVE-2026-4598 Infinite Loop in Kjur Jsrsasign Mar 23, 2026
- Critical CVE-2026-4599 Versions of the package jsrsasign from 7.0.0 and before 11.1.1 are vulnerable to… Mar 23, 2026
- Critical CVE-2026-4600 Improper Verification of Cryptographic Signature in Kjur Jsrsasign Mar 23, 2026
- Critical CVE-2026-4601 Versions of the package jsrsasign before 11.1.1 are vulnerable to Missing Cryptographic… Mar 23, 2026
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-4602 is "Versions of the package jsrsasign before 11.1.1 are vulnerable to Incorrect Conversion…", rated High. It affects Jsrsasign (Kjur); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.5 describes technical severity. EPSS 0.88% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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