CVE-2022-24771: Digitalbazaar Forge Signature Forgery Flaw

CVE-2022-24771 Overview

CVE-2022-24771 is a cryptographic signature verification vulnerability in Forge (also called node-forge), a native JavaScript implementation of Transport Layer Security (TLS). Prior to version 1.3.0, the RSA PKCS#1 v1.5 signature verification code exhibits lenient behavior when checking the digest algorithm structure. This weakness allows attackers to craft malicious structures that steal padding bytes and leverage unchecked portions of the PKCS#1 encoded message to forge signatures, particularly when a low public exponent is being used.

Critical Impact

Successful exploitation enables signature forgery attacks, potentially allowing attackers to bypass authentication mechanisms, impersonate trusted entities, or tamper with cryptographically signed data in applications relying on node-forge for RSA signature verification.

Affected Products

• Digitalbazaar Forge versions prior to 1.3.0
• Node.js applications using vulnerable node-forge packages
• Applications implementing RSA PKCS#1 v1.5 signature verification via forge

Discovery Timeline

• 2022-03-18 - CVE-2022-24771 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-24771

Vulnerability Analysis

This vulnerability stems from improper validation during RSA PKCS#1 v1.5 signature verification in the node-forge library. The signature verification process fails to strictly parse and validate the ASN.1-encoded DigestInfo structure, which contains the hash algorithm identifier and the message digest. This lenient parsing allows attackers to manipulate the padding bytes and exploit unchecked regions within the PKCS#1 encoded message.

The attack is particularly effective when RSA keys use low public exponents (commonly e=3), as the mathematical properties make it easier to construct forged signatures that pass the flawed verification. This is a variant of the Bleichenbacher signature forgery attack, which has historically affected multiple implementations of PKCS#1 v1.5.

Root Cause

The root cause is improper cryptographic signature verification (CWE-347) in the ASN.1 parsing and signature verification routines. Specifically, the library did not enforce strict parsing of all bytes in the PKCS#1 encoded message structure, allowing trailing garbage bytes and malformed structures to be accepted as valid. The ASN.1 decoder lacked a parseAllBytes option to ensure complete validation of the input data.

Attack Vector

The attack is network-accessible and requires no authentication or user interaction. An attacker can exploit this vulnerability by:

1. Identifying an application using a vulnerable version of node-forge for RSA signature verification
2. Crafting a specially structured PKCS#1 v1.5 encoded message with manipulated padding
3. Creating a forged signature that exploits the lenient ASN.1 parsing
4. Submitting the forged signature to bypass cryptographic verification

The following code shows the security patch that addresses this vulnerability by adding strict byte parsing:

  * @param [options] object with options or boolean strict flag
  *          [strict] true to be strict when checking value lengths, false to
  *            allow truncated values (default: true).
+ *          [parseAllBytes] true to ensure all bytes are parsed
+ *            (default: true)
  *          [decodeBitStrings] true to attempt to decode the content of
  *            BIT STRINGs (not OCTET STRINGs) using strict mode. Note that
  *            without schema support to understand the data context this can
  *            erroneously decode values that happen to be valid ASN.1. This
  *            flag will be deprecated or removed as soon as schema support is
  *            available. (default: true)
  *
+ * @throws Will throw an error for various malformed input conditions.
+ *
  * @return the parsed asn1 object.
  */
 asn1.fromDer = function(bytes, options) {
   if(options === undefined) {
     options = {
       strict: true,
+      parseAllBytes: true,
       decodeBitStrings: true
     };
   }
   if(typeof options === 'boolean') {
     options = {
       strict: options,
+      parseAllBytes: true,
       decodeBitStrings: true
     };

Source: GitHub Commit Change

Additional OID registration was added to properly handle hash algorithms:

 _IN('2.16.840.1.101.3.4.2.1', 'sha256');
 _IN('2.16.840.1.101.3.4.2.2', 'sha384');
 _IN('2.16.840.1.101.3.4.2.3', 'sha512');
+_IN('1.2.840.113549.2.2', 'md2');
 _IN('1.2.840.113549.2.5', 'md5');

 // pkcs#7 content types

Source: GitHub Commit Change

Detection Methods for CVE-2022-24771

Indicators of Compromise

• Unexpected authentication successes with malformed or suspicious certificate signatures
• Anomalous signature verification attempts with unusual padding patterns in PKCS#1 structures
• Log entries indicating acceptance of signatures that should have been rejected
• Unusual certificate or token validation patterns in application logs

Detection Strategies

• Audit Node.js application dependencies using npm audit or yarn audit to identify vulnerable node-forge versions
• Implement Software Composition Analysis (SCA) tools to continuously monitor for vulnerable packages
• Review application logs for signature verification anomalies or unexpected authentication patterns
• Deploy runtime application monitoring to detect unusual cryptographic operation patterns

Monitoring Recommendations

• Configure dependency scanning in CI/CD pipelines to block deployments with vulnerable node-forge versions
• Enable verbose logging for cryptographic operations to capture signature verification details
• Monitor for security advisories from the node-forge project and npm security feeds
• Implement alerting on unexpected signature verification failures or successes in production environments

How to Mitigate CVE-2022-24771

Immediate Actions Required

• Upgrade node-forge to version 1.3.0 or later immediately
• Audit all applications and dependencies for usage of vulnerable node-forge versions
• Review authentication and signature verification logs for potential exploitation attempts
• Consider temporary service restrictions if immediate patching is not possible

Patch Information

The vulnerability has been addressed in node-forge version 1.3.0. The fix introduces a parseAllBytes option in the ASN.1 decoder that defaults to true, ensuring all bytes in the encoded message are strictly validated. Additionally, the patch adds proper error throwing for malformed input conditions.

Update instructions:

npm update node-forge
# or
yarn upgrade node-forge

Verify the installed version:

npm list node-forge

For detailed patch information, see the GitHub Security Advisory.

Workarounds

• There are currently no known workarounds for this vulnerability according to the vendor advisory
• The only effective mitigation is upgrading to version 1.3.0 or later
• Consider implementing additional signature validation layers at the application level as defense-in-depth
• If upgrading is not immediately possible, evaluate restricting RSA key configurations to avoid low public exponents

# Configuration example
# Verify and update node-forge in package.json
npm install node-forge@^1.3.0 --save

# Run security audit to confirm remediation
npm audit --audit-level=high

# Lock dependencies to prevent regression
npm shrinkwrap