The nextBytes function in the SecureRandom class in Symfony before 2.3.37, 2.6.x before 2.6.13, and 2.7.x before 2.7.9 does not properly generate random numbers when used with PHP 5.x without the paragonie/randomcompat library and the opensslrandompseudobytes function fails, which makes it easier for attackers to defeat cryptographic protection mechanisms via unspecified vectors.