RSA-PSS signature validation vulnerability by prepending zeros in jsrsasign

CRITICAL 9.8CVE-2020-14968 · GHSA-q3gh-5r98-j4h3 · Published 22/06/2020 · updated 22/06/2026

In short

CVE-2020-14968 is a CRITICAL (CVSS 9.8) vulnerability affecting jsrsasign (kjur), jsrsasign.
Chance of exploitation in the next 30 days (EPSS): 2.9%, higher than 86.8% of all vulnerabilities.
Fix: update to 8.0.17 or later.

Package	Affected versions	Patched versions
jsrsasign kjur	`< 8.0.17`	`8.0.17`
jsrsasign npm	`≥ 3.0.0, < 8.0.17`	`8.0.17`

Description

Impact

Jsrsasign can verify RSA-PSS signature which value can expressed as BigInteger. When there is a valid RSA-PSS signature value, this vulnerability is also accept value with prepending zeros as a valid signature.

If you are not use RSA-PSS signature validation, this vulnerability is not affected.
Risk to accept a forged or crafted message to be signed is low.
Risk to raise memory corruption is low since jsrsasign uses BigInteger class.

Patches

Users using RSA-PSS signature validation should upgrade to 8.0.17.

Workarounds

Reject RSA-PSS signatures with unnecessary prepending zeros.

References

https://github.com/kjur/jsrsasign/security/advisories/GHSA-q3gh-5r98-j4h3 https://github.com/kjur/jsrsasign/issues/438 https://nvd.nist.gov/vuln/detail/CVE-2020-14968 https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-14968 https://vuldb.com/?id.157125 https://kjur.github.io/jsrsasign/api/symbols/RSAKey.html#.verifyWithMessageHashPSS

NVD description

An issue was discovered in the jsrsasign package before 8.0.17 for Node.js. Its RSASSA-PSS (RSA-PSS) implementation does not detect signature manipulation/modification by prepending '\0' bytes to a signature (it accepts these modified signatures as valid). An attacker can abuse this behavior in an application by creating multiple valid signatures where only one signature should exist. Also, an attacker might prepend these bytes with the goal of triggering memory corruption issues.

References

kjur/jsrsasign security advisory · WEB
nvd.nist.gov/vuln/detail/CVE-2020-14968 · ADVISORY
kjur/jsrsasign · WEB
kjur/jsrsasign commit 3bcc088 · WEB
cve.mitre.org/cgi-bin/cvename.cgi · WEB
kjur/jsrsasign · PACKAGE
kjur/jsrsasign release 8.0.17 · WEB
kjur/jsrsasign release 8.0.18 · WEB
kjur.github.io/jsrsasign · WEB
kjur.github.io/jsrsasign/api/symbols/RSAKey.html · WEB
security.netapp.com/advisory/ntap-20200724-0001 · WEB
vuldb.com · WEB
npmjs.com/advisories/1541

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Package

Affected versions

Patched versions

jsrsasign

kjur

< 8.0.17

8.0.17

jsrsasign

npm

≥ 3.0.0, < 8.0.17

8.0.17

Description

Impact

If you are not use RSA-PSS signature validation, this vulnerability is not affected.
Risk to accept a forged or crafted message to be signed is low.
Risk to raise memory corruption is low since jsrsasign uses BigInteger class.

Patches

Users using RSA-PSS signature validation should upgrade to 8.0.17.

Workarounds

Reject RSA-PSS signatures with unnecessary prepending zeros.

References

NVD description

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