PatchSiren

PatchSiren cyber security CVE debrief

CVE-2026-4601 kjur CVE debrief

CVE-2026-4601 is a HIGH-severity vulnerability (CVSS Score: 8.8) affecting jsrsasign versions before 11.1.1. The vulnerability stems from a missing cryptographic step in the DSA signing implementation, specifically in the KJUR.crypto.DSA.signWithMessageHash process. An attacker can exploit this by forcing 'r' or 's' to be zero, causing the library to emit an invalid signature without retrying, allowing the attacker to solve for 'x' from the resulting signature and potentially recover the private key. This issue impacts users of jsrsasign in Node.js environments. Defenders should prioritize patching due to the high severity and potential for private key recovery.

Vendor
kjur
Product
jsrsasign
CVSS
HIGH 8.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-03-23
Original CVE updated
2026-09-10
Advisory published
2026-03-23
Advisory updated
2026-09-10

Who should care

Developers and security teams using jsrsasign in Node.js applications should be aware of this vulnerability. Given the high CVSS score of 8.8, organizations should treat this as a priority issue, especially if their applications handle sensitive data or cryptographic operations. The vulnerability's impact on cryptographic integrity and potential for private key recovery make it critical for teams responsible for cryptographic security and key management.

Technical summary

The vulnerability (CVE-2026-4601) arises from a flaw in the DSA signing implementation of jsrsasign, specifically in the KJUR.crypto.DSA.signWithMessageHash process. When generating a DSA signature, the process failed to handle cases where 'r' or 's' equals zero properly, leading to the emission of invalid signatures without retrying. This oversight allows an attacker to manipulate the signature generation to solve for 'x', which is part of the private key, potentially enabling private key recovery. The issue affects all versions of jsrsasign prior to 11.1.1.

Defensive priority

High priority due to potential for private key recovery and high CVSS score.

Recommended defensive actions

  • Upgrade jsrsasign to version 11.1.1 or later to patch the vulnerability.
  • Review and update affected Node.js applications that use vulnerable jsrsasign versions.
  • Implement compensating controls such as additional signature verification steps.
  • Monitor for and respond to potential exploitation attempts.
  • Inventory and track usage of jsrsasign in your environment.

Evidence notes

The primary evidence for this vulnerability comes from the NVD and CVE records. The vulnerability affects jsrsasign versions before 11.1.1. Defenders should verify the version of jsrsasign used in their Node.js applications and check for any existing signatures that may have been generated using the vulnerable process. Official sources indicate that upgrading to version 11.1.1 or later mitigates this issue.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-4601 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-4601

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-4601 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-4601

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.