CVE-2025-22376: Net::OAuth Perl Weak Nonce Vulnerability

CVE-2025-22376 Overview

CVE-2025-22376 is an Insecure Random Number Generation vulnerability affecting the Net::OAuth package for Perl. In Net::OAuth::Client, versions before 0.29 use Perl's built-in rand() function to generate a 32-bit integer for the OAuth nonce value. This approach is cryptographically weak, as rand() is a pseudo-random number generator (PRNG) not designed for security-sensitive operations.

OAuth nonces are critical security tokens designed to prevent replay attacks by ensuring each request is unique. Using a predictable random number generator undermines this protection, potentially allowing attackers to predict nonce values and replay authenticated requests.

Critical Impact

Attackers may predict OAuth nonce values, enabling replay attacks against OAuth-protected APIs and services using the vulnerable Net::OAuth package.

Affected Products

• Net::OAuth package for Perl versions prior to 0.29
• Applications using Net::OAuth::Client for OAuth authentication
• Systems implementing OAuth 1.0/1.0a using the vulnerable library

Discovery Timeline

• 2025-01-03 - CVE-2025-22376 published to NVD
• 2025-01-21 - Last updated in NVD database

Technical Details for CVE-2025-22376

Vulnerability Analysis

The vulnerability stems from the use of Perl's rand() function for generating OAuth nonces. According to IETF RFC 5849 Section 3.3, the nonce is a random string uniquely generated by the client to allow the server to verify that a request has never been made before. The RFC further specifies in Section 4.10 that nonces should be unpredictable to prevent attackers from calculating future nonce values.

The rand() function in Perl is a linear congruential generator (LCG) designed for general-purpose randomness, not cryptographic security. Its output is deterministic given the seed, and with only 32 bits of entropy, the nonce space is limited to approximately 4.3 billion possible values—easily brute-forceable with modern computing resources.

Root Cause

The root cause is classified under CWE-338 (Use of Cryptographically Weak Pseudo-Random Number Generator). The vulnerable code in Net::OAuth::Client at line 260 generates the nonce using int(rand(2**32)), which produces predictable values that fail to meet cryptographic randomness requirements for OAuth security tokens.

Attack Vector

This vulnerability is exploitable over the network without authentication. An attacker could:

1. Observe OAuth requests to identify the nonce pattern
2. Predict future nonce values using the weak PRNG characteristics
3. Craft replay attacks by reusing captured OAuth signatures with predicted nonces
4. Bypass OAuth security controls to perform unauthorized API operations

The fix introduced in version 0.29 replaces the weak rand() call with cryptographically secure randomness from Crypt::URandom:

         'Class::Data::Inheritable' => '0.06',
         'Encode' => '2.35',
         'LWP::UserAgent' => '1',
+        'Crypt::URandom' => '0.37',
     },
     configure_requires => {
         'Module::Build'         => '0.4234',

Source: GitHub Net-OAuth Commit 2aa25e

Detection Methods for CVE-2025-22376

Indicators of Compromise

• Repeated OAuth authentication attempts with sequential or predictable nonce values in access logs
• Unusual patterns of OAuth token usage indicating potential replay attacks
• Multiple successful API calls with similar timestamps and nonce collision patterns

Detection Strategies

• Audit Perl dependencies using cpanm --showdeps Net::OAuth to identify vulnerable versions prior to 0.29
• Implement server-side nonce tracking to detect duplicate or sequential nonce submissions
• Review application logs for OAuth signature validation failures that may indicate replay attempts
• Use software composition analysis (SCA) tools to flag vulnerable Net::OAuth installations

Monitoring Recommendations

• Enable detailed OAuth request logging to capture nonce values for pattern analysis
• Configure alerts for OAuth authentication anomalies such as rapid request rates or nonce collisions
• Monitor for the presence of Crypt::URandom dependency as an indicator of the patched version

How to Mitigate CVE-2025-22376

Immediate Actions Required

• Upgrade Net::OAuth to version 0.29 or later immediately
• Audit all applications using Net::OAuth::Client for OAuth authentication
• Review recent OAuth logs for signs of replay attacks against affected systems
• Consider rotating OAuth credentials for applications that were running vulnerable versions

Patch Information

The security patch is available in Net::OAuth version 0.29. The fix introduces Crypt::URandom as a dependency to provide cryptographically secure random number generation for nonce creation. The changelog documents the security improvement:

       [Security]
       - Net::OAuth::Client uses a better source of randomness for generating the nonce

        [Bug Fixes]
        - Removed unnecessary prerequisite RT#69810 GH#4 GH#6
        - Fix broken dependency for URI::Escape GH#4 (thanks oiami)

Source: GitHub Net-OAuth Commit 2aa25e

Workarounds

• Implement server-side nonce validation with strict uniqueness checking and short expiration windows
• Add rate limiting on OAuth endpoints to reduce the effectiveness of brute-force nonce prediction
• Consider implementing additional request signing mechanisms beyond standard OAuth 1.0 nonces

# Upgrade Net::OAuth to patched version
cpanm Net::OAuth@0.29

# Verify installed version
perl -MNet::OAuth -e 'print $Net::OAuth::VERSION'

# Check for Crypt::URandom dependency (indicates patched version)
perl -MCrypt::URandom -e 'print "Crypt::URandom available\n"'