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CVE-2026-33894 is a critical cryptographic signature verification vulnerability affecting the node-forge library, a native JavaScript implementation of Transport Layer Security and cryptographic protocols.
The vulnerability operates as a sophisticated variant of the classic Bleichenbacher signature forgery attack targeting the RSASSA PKCS1 v1.5 signature verification algorithm.
Specifically, the flaw arises from improper input validation and lax parsing logic within the ASN.1-encoded DigestInfo structure embedded inside digital signatures.
When an application utilizes node-forge for cryptographic verification with low public exponent RSA keys, the parser fails to rigorously check structural boundaries.
It permits extraneous or malformed trailing data within the ASN.1 structure that should normally trigger an immediate rejection by standard-compliant engines.
Furthermore, the library fails to enforce the mandatory PKCS1 specification requirement demanding a minimum of 8 bytes of 0xFF padding blocks.
By exploiting these validation oversights, an attacker can construct a mathematical value which, when raised to the low public exponent, results in a valid bit pattern.
Because the parser overlooks the absent 0xFF padding requirements and accepts relaxed ASN.1 framing, the forged signature successfully passes validation checks.
This allows malicious actors to completely bypass authentication mechanisms, forge software updates, or compromise document integrity without possessing the private key.
The vulnerability requires network access and zero user interaction, making it highly dangerous for server-side JavaScript applications relying on vulnerable configurations.
DailyCVE Form:
Platform: node-forge library
Version: Below 1.4.0
Vulnerability: Authentication bypass
Severity: High risk
date: April 2 2026
Prediction: Patched in April
What Undercode Say:
Bash Commands And Code
npm install [email protected] node -e "const forge = require('node-forge'); console.log(forge.VERSION);"
Exploit: (Educational Purposes!)
const forge = require('node-forge');
const publicKey = forge.pki.setRsaPublicKey(bigIntExp, bigIntMod);
const verified = publicKey.verify(digest, forgedSignature, 'RSASSA-PKCS1-V1_5');
console.log('Verification result:', verified);
Protection: from this CVE
Upgrade the node-forge package immediately to version 1.4.0 or later to enforce strict ASN.1 parsing and mandatory 8-byte padding validations. Avoid using low public exponent RSA keys and implement alternative multi-layered cryptographic verification protocols where feasible.
Impact:
Successful exploitation allows remote unauthenticated attackers to forge digital signatures, bypass cryptographic authentication controls, spoof software updates, and compromise integrity checks across vulnerable JavaScript and Node.js ecosystems.
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Sources:
Reported By: github.com
Extra Source Hub:
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