An issue was discovered in PHP 7.3.x before 7.3.0alpha3, 7.2.x before 7.2.8, and before 7.1.20. The php-fpm master process restarts a child process in an endless loop when using program execution functions (e.g., passthru, exec, shell_exec, or system) with a non-blocking STDIN stream, causing this master process to consume 100% of the CPU, and consume disk space with a large volume of error logs, as demonstrated by an attack by a customer of a shared-hosting facility.
The MITRE CVE dictionary describes this issue as:
Find out more about CVE-2015-9253 from the MITRE CVE dictionary dictionary and NIST NVD.
The Red Hat Product Security Team does not consider this issue as a security flaw because specially crafted PHP scripts (containing embedded operating system commands) are required to trigger this flaw.
NOTE: The following CVSS v3 metrics and score provided are preliminary and subject to review.
| CVSS3 Base Score | 7.5 |
|---|---|
| CVSS3 Base Metrics | CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| Attack Vector | Network |
| Attack Complexity | Low |
| Privileges Required | None |
| User Interaction | None |
| Scope | Unchanged |
| Confidentiality | None |
| Integrity Impact | None |
| Availability Impact | High |
| Platform | Package | State |
|---|---|---|
| Red Hat Software Collections for Red Hat Enterprise Linux | rh-php70-php | Not affected |
| Red Hat Software Collections for Red Hat Enterprise Linux | rh-php56-php | Not affected |
| Red Hat Software Collections for Red Hat Enterprise Linux | rh-php71-php | Not affected |
| Red Hat Enterprise Linux 7 | php | Not affected |
| Red Hat Enterprise Linux 6 | php | Not affected |
| Red Hat Enterprise Linux 5 | php53 | Not affected |
| Red Hat Enterprise Linux 5 | php | Not affected |
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