Summary
Workarounds
There is no workaround. Not to use RSA signature validation in jsrsasign.
ACKNOWLEDGEMENT
Thanks to Daniel Yahyazadeh @yahyazadeh for reporting and analyzing this vulnerability.
Impact
Vulnerable jsrsasign will accept RSA signature with improper PKCS#1.5 padding.
Decoded RSA signature value consists following form:01(ff...(8 or more ffs)...ff)00[ASN.1 OF DigestInfo]
Its byte length must be the same as RSA key length, however such checking was not sufficient.
To make crafted message for practical attack is very hard.
CVE-2021-30246 has a CVSS score of 9.1 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (10.2.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
Users validating RSA signature should upgrade to 10.2.0 or later.
Frequently Asked Questions
- What is CVE-2021-30246? CVE-2021-30246 is a critical-severity security vulnerability in jsrsasign (npm), affecting versions < 10.2.0. It is fixed in 10.2.0.
- How severe is CVE-2021-30246? CVE-2021-30246 has a CVSS score of 9.1 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of jsrsasign are affected by CVE-2021-30246? jsrsasign (npm) versions < 10.2.0 is affected.
- Is there a fix for CVE-2021-30246? Yes. CVE-2021-30246 is fixed in 10.2.0. Upgrade to this version or later.
- Is CVE-2021-30246 exploitable, and should I be worried? Whether CVE-2021-30246 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2021-30246 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2021-30246? Upgrade
jsrsasignto 10.2.0 or later.