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A Vulnerability in PHP Could Allow for Arbitrary Code Execution

MS-ISAC ADVISORY NUMBER:

2019-101

DATE(S) ISSUED:

09/27/2019

OVERVIEW:

A vulnerability has been discovered in PHP, which could allow an attacker to execute arbitrary code. PHP is a programming language originally designed for use in web-based applications with HTML content. PHP supports a wide variety of platforms and is used by numerous web-based software applications. Successfully exploiting this vulnerability could allow for arbitrary code execution in the context of the affected application. Depending on the privileges associated with the application, an attacker could install programs; view, change, or delete data; or create new accounts with full user rights. Failed exploitation could result in a denial-of-service condition.

THREAT INTELLIGENCE:

There are currently no reports of this vulnerability being exploited in the wild.

SYSTEMS AFFECTED:

  • PHP versions 7.3 prior to 7.3.10

RISK:

Government:
  • Large and medium government entities: HIGH
  • Small government entities: HIGH
Businesses:
  • Large and medium business entities: HIGH
  • Small business entities: HIGH
Home Users:
LOW

TECHNICAL SUMMARY:

A vulnerability has been discovered in PHP, which could allow an attacker to execute arbitrary code. PHP is prone to a heap-based buffer-overflow vulnerability because the application fails to properly bounds-check user-supplied data before copying it into an insufficiently sized buffer. Specifically, this issue exists in the 'mb_eregi()' function.

Version 7.3.10

  • Bug #78559 (Heap Buffer Overflow in mb_eregi).

Successfully exploiting this vulnerability could allow for arbitrary code execution in the context of the affected application. Depending on the privileges associated with the application, an attacker could install programs; view, change, or delete data; or create new accounts with full user rights. Failed exploitation could result in a denial-of-service condition.

RECOMMENDATIONS:

We recommend the following actions be taken:

  • Upgrade to the latest version of PHP immediately, after appropriate testing.
  • Verify no unauthorized system modifications have occurred on system before applying patch.
  • Apply the principle of Least Privilege to all systems and services.
  • Remind users not to visit websites or follow links provided by unknown or untrusted sources.

REFERENCES:

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