#VU10335 Improper input validation in PHP - CVE-2017-8923

Vulnerability identifier: #VU10335

Vulnerability risk: Low

CVSSv4.0: 4.6 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2017-8923

CWE-ID: CWE-20

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
PHP
Universal components / Libraries / Scripting languages

Vendor: PHP Group

Description
The vulnerability allows a remote attacker to perform denial of service (DoS) attack.

The vulnerability exists due to insufficient input validation in zend_string_extend() function in Zend/zend_string.h when leveraging a script's use of ".=" with a long. The application does not prevent changes to string objects that can result in a negative length. A remote attacker can pass an overly long string to script, which uses ".=" operand on the supplied data and trigger application crash.

Mitigation
Update to version 5.6.31, 7.0.20 or 7.1.6.

Vulnerable software versions

PHP: 5.5.0 - 5.5.38, 5.6.0 - 5.6.30, 7.0.0 - 7.0.19, 7.1.0 - 7.1.5

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External links
https://bugs.php.net/bug.php?id=74577
https://bugs.php.net/bug.php?id=73122

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.