CVE-2023-0567: 
PHP vulnerability analysis and mitigation

CVE-2023-0567 affects PHP versions 8.0.X before 8.0.28, 8.1.X before 8.1.16, and 8.2.X before 8.2.3. The vulnerability exists in the password_verify() function, which may incorrectly accept some invalid Blowfish hashes as valid (NVD, Ubuntu).

The vulnerability is caused by a PHP-specific modification to the crypt_blowfish implementation called 'PHP hack' that allows a salt cut short by $ to be detected as valid. This can trigger a buffer overread when copying the setting into the output buffer, as the memcpy uses fixed sizes even if the setting might be too short. The issue specifically affects malformatted BCrypt hashes that include a $ within their salt part (GitHub Advisory).

If an invalid hash ends up in the password database, it may lead to an application accepting any password as valid for that entry. This could potentially allow unauthorized access to affected systems if an attacker manages to inject malformed hashes into the password database (Red Hat).

The vulnerability has been fixed in PHP versions 8.0.28, 8.1.16, and 8.2.3. Users should upgrade to these or later versions to address the issue. The fix involves removing the 'PHP Hack' and aligning PHP's crypt_blowfish implementation with Openwall's implementation (GitHub Advisory).