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RSA PKCS#1 decryption vulnerability with prepending zeros in jsrsasign

Critical severity GitHub Reviewed Published Jun 23, 2020 in kjur/jsrsasign • Updated Jan 31, 2023

Package

npm jsrsasign (npm)

Affected versions

< 8.0.18

Patched versions

8.0.18

Description

Impact

Jsrsasign supports RSA PKCS#1 v1.5 (i.e. RSAES-PKCS1-v1_5) 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-v1_5 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-v1_5 or RSA-OAEP decryption should upgrade to 8.0.18.

Workarounds

Reject RSA PKCS1-v1_5 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
kjur/jsrsasign#439

References

Published by the National Vulnerability Database Jun 22, 2020
@kjur kjur published to kjur/jsrsasign Jun 23, 2020
Reviewed Jun 26, 2020
Published to the GitHub Advisory Database Jun 26, 2020
Last updated Jan 31, 2023

Severity

Critical

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS score

1.634%
(88th percentile)

Weaknesses

CVE ID

CVE-2020-14967

GHSA ID

GHSA-xxxq-chmp-67g4

Source code

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