CVE-2021-30246
RSA signature validation vulnerability on maleable encoded message in jsrsasign
In the jsrsasign package through 10.1.13 for Node.js, some invalid RSA PKCS#1 v1.5 signatures are mistakenly recognized to be valid. NOTE: there is no known practical attack.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
NVD Score used
In the jsrsasign package through 10.1.13 for Node.js, some invalid RSA PKCS#1 v1.5 signatures are mistakenly recognized to be valid. NOTE: there is no known practical attack.
- Record
CVE-2021-30246- CVSS 3.1
- 9.1 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N - CVSS 2.0
- 6.4 Medium
AV:N/AC:L/Au:N/C:P/I:P/A:N - Weakness
- CWE-347
- Updated
- 2026-11-02
CVE List No score
In the jsrsasign package through 10.1.13 for Node.js, some invalid RSA PKCS#1 v1.5 signatures are mistakenly recognized to be valid. NOTE: there is no known practical attack.
- Record
CVE-2021-30246- Updated
- 2026-11-02
EUVDEUVD-2021-0736 No score
In the jsrsasign package through 10.1.13 for Node.js, some invalid RSA PKCS#1 v1.5 signatures are mistakenly recognized to be valid. NOTE: there is no known practical attack.
- Record
EUVD-2021-0736- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-27fj-mc8w-j9wg
RSA signature validation vulnerability on maleable encoded message in jsrsasign
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.
Patches
Users validating RSA signature should upgrade to 10.2.0 or later.
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.
- Record
GHSA-27fj-mc8w-j9wg- CVSS 3.1
- 9.1 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N - Weakness
- CWE-347
- Updated
- 2026-11-02
OSV
In the jsrsasign package through 10.1.13 for Node.js, some invalid RSA PKCS#1 v1.5 signatures are mistakenly recognized to be valid. NOTE: there is no known practical attack.
- Record
CVE-2021-30246- CVSS 3.1
- 9.1 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N - Updated
- 2026-11-02
OSVGHSA-27fj-mc8w-j9wg
RSA signature validation vulnerability on maleable encoded message in jsrsasign
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.
Patches
Users validating RSA signature should upgrade to 10.2.0 or later.
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.
- Record
GHSA-27fj-mc8w-j9wg- CVSS 3.1
- 9.1 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N - Weakness
- CWE-347
- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
jsrsasignnpm |
before 10.2.0 | 10.2.0 |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-30246 is a critical vulnerability (CVSS 9.1) in Kjur Jsrsasign, published April 7, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.96%, the 61st percentile. Fixed in jsrsasign 10.2.0.