CVE-2026-17544 in PHP
Summary
by MITRE • 07/30/2026
Attacker-provided inputs to bccomp() could lead to an out-of-bounds write with stack and heap corruption in PHP versions from 8.4.* before 8.4.24 and from 8.5.* before 8.5.9.
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Analysis
by VulDB Data Team • 07/30/2026
The vulnerability in question affects the bccomp() function within PHP, a critical component for handling arbitrary precision arithmetic operations. This flaw represents a serious security concern that can be exploited through attacker-provided inputs to achieve out-of-bounds write conditions resulting in stack and heap corruption. The vulnerability is present in specific PHP version ranges including 8.4. versions prior to 8.4.24 and 8.5. versions prior to 8.5.9, indicating a targeted issue that affects the mathematical computation library within the PHP runtime environment.
The technical nature of this vulnerability stems from improper input validation and memory management within the bccomp() function implementation. When processing attacker-controlled data, the function fails to properly bounds-check array accesses or buffer operations, leading to memory corruption that can be leveraged for arbitrary code execution. This type of flaw falls under CWE-129 Input Validation and OWASP Top Ten category A03: Injection, specifically manifesting as an out-of-bounds write condition that can compromise the memory integrity of the PHP process. The vulnerability operates at the intersection of arithmetic computation and memory safety, where mathematical operations involving large numbers or malformed inputs trigger buffer overflow conditions.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to potentially enable remote code execution attacks. Attackers can craft malicious input sequences that cause the bccomp() function to write data beyond allocated memory boundaries, corrupting adjacent stack variables or heap memory regions. This corruption can lead to unpredictable program behavior, application crashes, or more severe exploitation outcomes including privilege escalation and system compromise. The vulnerability's exploitation potential is heightened by PHP's widespread use in web applications where user inputs are frequently processed through mathematical functions for financial calculations, cryptographic operations, or scientific computations.
Mitigation strategies for this vulnerability require immediate patching of affected PHP installations to versions 8.4.24 or later and 8.5.9 or later, which contain the necessary code fixes for proper bounds checking in the bccomp() function. System administrators should also implement input validation measures to sanitize any data processed through arithmetic functions, particularly when dealing with user-supplied inputs that may be passed to bccomp() operations. Additional defensive measures include implementing runtime protections such as address space layout randomization ASLR, stack canaries, and heap metadata protection where available. Organizations should monitor their PHP application environments for any signs of exploitation attempts and maintain comprehensive logging of arithmetic function calls to detect anomalous usage patterns that may indicate exploitation activity. The vulnerability demonstrates the critical importance of proper memory management in mathematical computation libraries and highlights the need for regular security auditing of core PHP functions that handle user-provided data.