RSA signature validation vulnerability on maleable encoded message in jsrsasign

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

9.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS

• CVE-2021-30246: 0.96% estimated exploitation activity in the next 30 days; percentile 61.59 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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.

Published by the source

16 Apr 2021, 19:52 UTC

Last modified by the source

8 Nov 2023, 04:05 UTC

Source last checked

26 Oct 2026, 12:26 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-27fj-mc8w-j9wg

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-27fj-mc8w-j9wg

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# Patch Next advisory brief: CVE-2021-30246

Advisory: RSA signature validation vulnerability on maleable encoded message in jsrsasign
IDs: CVE-2021-30246, GHSA-27fj-mc8w-j9wg
Record: https://patchnext.com/advisories/cve-2021-30246 (revision 2, source checked 26 Oct 2026, 12:26 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: jsrsasign 10.2.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm jsrsasign: affected < 10.2.0; fixed in 10.2.0

## Suggested inspection (read-only)
- `npm ls jsrsasign --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on jsrsasign.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-27fj-mc8w-j9wg (OSV record GHSA-27fj-mc8w-j9wg lists affected ranges: npm jsrsasign >=0 <10.2.0 (fixed))
- Verified: https://github.com/advisories/GHSA-27fj-mc8w-j9wg (GitHub-reviewed advisory GHSA-27fj-mc8w-j9wg lists affected ranges: npm jsrsasign >=0 <10.2.0)

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