CVE-2026-5088: Apache::API::Password Weak Salt Vulnerability

CVE-2026-5088 Overview

Apache::API::Password versions through v0.5.2 for Perl contain an insecure random number generation vulnerability in the password salt generation mechanism. The _make_salt and _make_salt_bcrypt methods attempt to load cryptographically secure random number generators (Crypt::URandom or Bytes::Random::Secure), but fall back to using Perl's built-in rand function when these modules are unavailable. Since rand is not designed for cryptographic use, this creates a significant security weakness where password salts become predictable, potentially enabling offline password cracking attacks.

Critical Impact

Weak salt generation using Perl's rand function allows attackers to predict password salts, making password hashes significantly easier to crack through brute force or rainbow table attacks.

Affected Products

• Apache2::API v0.5.2 and earlier versions
• Systems running Apache2::API without Crypt::URandom module installed
• Systems running Apache2::API without Bytes::Random::Secure module installed

Discovery Timeline

• 2026-04-15 - CVE-2026-5088 published to NVD
• 2026-04-16 - Last updated in NVD database

Technical Details for CVE-2026-5088

Vulnerability Analysis

This vulnerability is classified as CWE-338 (Use of Cryptographically Weak Pseudo-Random Number Generator). The core issue lies in the fallback behavior of the salt generation functions within the Apache2::API Password module.

When the preferred cryptographically secure random number generators (Crypt::URandom or Bytes::Random::Secure) are not available on the system, the module silently degrades to using Perl's rand function to generate 16 bytes of salt data. Perl's rand function is a linear congruential generator (LCG) that is deterministic and predictable when seeded, making it entirely unsuitable for security-sensitive operations like password salt generation.

The practical impact is that an attacker who knows or can guess the state of the random number generator could predict future salts. This dramatically reduces the effectiveness of password hashing, as salts are specifically designed to prevent precomputed attacks (rainbow tables) and ensure identical passwords produce different hashes.

Root Cause

The root cause is a design decision to implement graceful degradation without proper security warnings. The _make_salt and _make_salt_bcrypt methods follow a fallback chain:

1. First, attempt to use Crypt::URandom for cryptographically secure random bytes
2. If unavailable, attempt to use Bytes::Random::Secure
3. If both are unavailable, fall back to rand() without warning the user

This silent fallback creates a dangerous situation where administrators may believe their password hashing is secure when it is not. The vulnerability is particularly insidious because it only manifests when specific Perl modules are missing, which may not be immediately apparent during deployment.

Attack Vector

The vulnerability is exploitable over the network without authentication. An attacker could exploit this weakness through the following approach:

The attack methodology involves first identifying systems running vulnerable Apache2::API versions without the required secure random modules installed. Once identified, the attacker would need to obtain password hashes (through SQL injection, data breach, or other means). With knowledge that weak salts were used, the attacker can then mount more efficient offline attacks against the hashes.

Because rand() is seeded from a limited entropy source and follows a predictable sequence, an attacker can potentially reconstruct the salt values used for password hashing. This is especially effective if the attacker can observe or influence the system state around the time passwords were created or updated.

For technical details on proper random data generation for security purposes, refer to the MetaCPAN Guide on Random Data Security.

Detection Methods for CVE-2026-5088

Indicators of Compromise

• Presence of Apache2::API versions v0.5.2 or earlier in Perl module installations
• Absence of Crypt::URandom and Bytes::Random::Secure modules on systems using Apache2::API
• Log entries indicating password hashing operations without secure random module availability
• Unexpectedly weak or predictable salt patterns in stored password hashes

Detection Strategies

• Audit Perl module installations using cpan -l or perldoc -l Apache2::API::Password to identify vulnerable versions
• Verify presence of cryptographically secure random modules: perl -MCrypt::URandom -e 1 and perl -MBytes::Random::Secure -e 1
• Review application logs for module loading failures related to random number generation
• Implement file integrity monitoring on Perl library directories to detect unauthorized downgrades

Monitoring Recommendations

• Monitor for password reset patterns that may indicate attackers testing cracked credentials
• Track authentication failures for signs of credential stuffing attacks targeting accounts with weak salts
• Alert on any installation or removal of Perl cryptographic modules
• Conduct periodic vulnerability scans focusing on Perl module version inventory

How to Mitigate CVE-2026-5088

Immediate Actions Required

• Upgrade Apache2::API to version v0.5.3 or later immediately
• Install Crypt::URandom module: cpan install Crypt::URandom
• Alternatively, install Bytes::Random::Secure module: cpan install Bytes::Random::Secure
• Force password resets for all users whose passwords were hashed with potentially weak salts
• Audit existing password hashes to identify those created during the vulnerable period

Patch Information

The vulnerability has been addressed in Apache2::API version v0.5.3. According to the MetaCPAN Apache2-API v0.5.3 Changes, the updated version resolves the insecure random number generation issue. Organizations should upgrade to this version or later as soon as possible.

The Apache2-API Password Documentation provides additional context on the module's password handling functionality.

Workarounds

• Ensure Crypt::URandom is installed before Apache2::API loads by adding it to deployment dependencies
• Add explicit module checks in application startup to fail fast if secure random modules are unavailable
• Implement application-level validation to verify cryptographically secure random generation is active
• Consider using alternative password hashing libraries that enforce secure random number generation without fallback

# Verify and install required cryptographic modules
# Check current Apache2::API version
perl -MApache2::API -e 'print $Apache2::API::VERSION'

# Install secure random module dependency
cpan install Crypt::URandom

# Verify the module loads correctly
perl -MCrypt::URandom -e 'print "Crypt::URandom available\n"'

# Upgrade to patched version
cpan install Apache2::API