RSA PKCS#1 decryption vulnerability with prepending zeros in jsrsasign

Exploitation

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

CVSS

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

EPSS

• CVE-2020-14967: 2.27% estimated exploitation activity in the next 30 days; percentile 83.08 (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 Jsrsasign supports RSA PKCS#1 v1.5 (i.e. RSAES-PKCS1-v15) and RSA-OAEP encryption and decryption. Its encrypted message is represented as BigInteger. When there is a valid encrypted message, a crafted message with prepending zeros can be decrypted by this vulnerability. - If you don't use RSA PKCS1-v15 or RSA-OAEP decryption, this vulnerability is not affected. - Risk to forge contents of encrypted message is very low. - Risk to raise memory corruption is low since jsrsasign uses BigInteger class. Patches Users using RSA PKCS1-v15 or RSA-OAEP decryption should upgrade to 8.0.18. Workarounds Reject RSA PKCS1-v15 or RSA-OAEP encrypted message with unnecessary prepending zeros. References https://nvd.nist.gov/vuln/detail/CVE-2020-14967 https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-14967 https://vuldb.com/?id.157124 https://kjur.github.io/jsrsasign/api/symbols/KJUR.crypto.Cipher.html#.decrypt https://github.com/kjur/jsrsasign/issues/439

Published by the source

26 Jun 2020, 16:27 UTC

Last modified by the source

8 Nov 2023, 04:02 UTC

Source last checked

26 Oct 2026, 12:17 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-xxxq-chmp-67g4

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-xxxq-chmp-67g4

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# Patch Next advisory brief: CVE-2020-14967

Advisory: RSA PKCS#1 decryption vulnerability with prepending zeros in jsrsasign
IDs: CVE-2020-14967, GHSA-xxxq-chmp-67g4
Record: https://patchnext.com/advisories/cve-2020-14967 (revision 2, source checked 26 Oct 2026, 12:17 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: jsrsasign 8.0.18. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm jsrsasign: affected < 8.0.18; fixed in 8.0.18

## 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-xxxq-chmp-67g4 (OSV record GHSA-xxxq-chmp-67g4 lists affected ranges: npm jsrsasign >=0 <8.0.18 (fixed))
- Verified: https://github.com/advisories/GHSA-xxxq-chmp-67g4 (GitHub-reviewed advisory GHSA-xxxq-chmp-67g4 lists affected ranges: npm jsrsasign >=0 <8.0.18)

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