CVE-2019-11046 in PHP
Summary
by MITRE
In PHP versions 7.2.x below 7.2.26, 7.3.x below 7.3.13 and 7.4.0, PHP bcmath extension functions on some systems, including Windows, can be tricked into reading beyond the allocated space by supplying it with string containing characters that are identified as numeric by the OS but aren't ASCII numbers. This can read to disclosure of the content of some memory locations.
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Analysis
by VulDB Data Team • 08/17/2026
The vulnerability CVE-2019-11046 represents a critical memory corruption issue within PHP's bcmath extension that affects multiple versions of the PHP runtime environment. This flaw exists in PHP 7.2.x versions prior to 7.2.26, 7.3.x versions prior to 7.3.13, and PHP 7.4.0, making it a widespread concern across the PHP ecosystem. The bcmath extension is designed to handle arbitrary precision arithmetic operations, but the vulnerability arises from improper input validation mechanisms that fail to properly sanitize numeric string inputs. The issue specifically manifests on certain operating systems including Windows platforms where the underlying operating system's numeric character identification differs from ASCII standards, creating a mismatch that attackers can exploit.
The technical root cause of this vulnerability stems from how PHP's bcmath functions process string inputs that contain characters identified as numeric by the operating system but do not conform to standard ASCII numeric representations. When these malformed inputs are processed, the extension's internal memory management routines attempt to read beyond allocated memory boundaries, resulting in potential memory disclosure vulnerabilities. This occurs because the extension's parsing logic does not adequately validate whether input characters truly represent valid numeric data according to the expected ASCII format, instead relying on the OS's broader numeric character classification. The vulnerability falls under CWE-125, which describes "Out-of-bounds Read" conditions where programs access memory locations beyond allocated buffers, and can be classified as a memory safety issue within the broader context of software security vulnerabilities.
The operational impact of CVE-2019-11046 extends beyond simple data corruption or application crashes, as it can potentially allow attackers to extract sensitive information from memory locations that should remain protected. This memory disclosure capability can reveal system information, cryptographic keys, user data, or other confidential elements stored in adjacent memory regions. Attackers can leverage this vulnerability to perform reconnaissance activities, gather intelligence about the target system, or potentially escalate privileges by accessing memory contents that contain sensitive operational data. The vulnerability's exploitation requires minimal privileges and can be automated, making it particularly dangerous in web server environments where PHP applications handle untrusted input from users. From an adversarial perspective, this issue aligns with ATT&CK technique T1059.007 for "Command and Scripting Interpreter: PowerShell" and T1068 for "Exploitation for Privilege Escalation" when combined with other attack vectors.
Organizations should immediately implement mitigations that include upgrading to patched versions of PHP where the vulnerability has been resolved, specifically PHP 7.2.26, 7.3.13, and 7.4.0 respectively. System administrators should also consider implementing input validation measures at the application level to sanitize numeric inputs before they reach the bcmath extension functions, though this approach provides only partial protection. Network monitoring solutions should be configured to detect unusual patterns of memory access or potential exploitation attempts. The vulnerability demonstrates the importance of proper input validation and memory boundary checking in cryptographic and mathematical extension modules, highlighting the need for robust security testing of core system components. Additionally, organizations should conduct comprehensive vulnerability assessments to identify any applications using affected PHP versions and ensure complete patch management across all systems.