CVE-2026-89158 in PCRE2
Summary
by MITRE • 09/11/2026
PCRE2 before 10.48, on 32-bit platforms, has a pcre2_compile_32 integer overflow and resultant out-of-bounds write.
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Analysis
by VulDB Data Team • 09/11/2026
The Perl Compatible Regular Expressions version two library, commonly referred to as PCRE2, is a widely adopted open-source software library that provides functions for matching text against regular expressions. It serves as the foundational regex engine for numerous high-profile applications and frameworks across various operating systems, including PHP, Apache HTTP Server, and many other security-critical tools. A critical vulnerability identified in versions prior to 10.48 involves a specific integer overflow condition within the pcre2_compile_32 function when executed on 32-bit computing platforms. This flaw represents a significant deviation from expected memory management protocols during the compilation phase of regular expression patterns, potentially leading to severe security consequences for systems relying on this library.
The technical root cause of this vulnerability lies in how PCRE2 allocates internal data structures required to compile and store compiled regex objects. During the parsing process, the library calculates the size of these structures based on input parameters derived from the regular expression pattern itself. On 32-bit architectures, where integer values are limited to a specific range before wrapping around, an attacker can craft a specially designed regular expression that triggers an arithmetic overflow during this calculation. Instead of allocating memory proportional to the actual complexity and size required by the regex, the library allocates a significantly smaller buffer due to the wrapped-around value being interpreted as a small positive integer rather than a large negative or erroneous magnitude.
This miscalculation results in a classic out-of-bounds write condition. When the compilation process proceeds, it attempts to populate the undersized allocated buffer with data that exceeds its boundaries. Because standard memory allocators do not always enforce strict bounds checking on heap allocations during such internal operations, this overflow allows an attacker to overwrite adjacent memory regions. Depending on the specific layout of the heap and the target application's use of PCRE2, these overwritten bytes may contain critical control data, function pointers, or object metadata. This scenario aligns directly with CWE-190, which defines integer overflows that can lead to other weaknesses such as buffer overflows, and CWE-787, which covers out-of-bounds writes in general contexts.
The operational impact of this vulnerability is severe, primarily because it facilitates remote code execution or denial of service attacks against any application that processes untrusted regular expression patterns without proper sanitization. If an attacker can supply a malicious regex pattern to a vulnerable version of PCRE2 running on a 32-bit system, they may achieve arbitrary memory write capabilities. This capability allows for the exploitation of further vulnerabilities within the host process, such as bypassing stack-based protections or manipulating control flow execution paths. In environments where regular expressions are processed from user input, this vulnerability effectively lowers the barrier to entry for successful exploitation, turning a simple string processing function into a potent attack vector.
From an adversary perspective, this flaw maps closely to techniques described in the MITRE ATT&CK framework, specifically those related to memory corruption and privilege escalation via buffer overflows. The ability to write outside allocated boundaries is often a precursor to more sophisticated attacks like heap spraying or arbitrary code execution through function pointer hijacking. Consequently, systems running 32-bit binaries that utilize PCRE2 for pattern matching are at heightened risk if they do not implement strict input validation on regex patterns before passing them to the library.
Mitigation strategies must focus primarily on upgrading the underlying software components. Organizations and developers should immediately update their installations of PCRE2 to version 10.48 or later, where this integer overflow has been patched by correcting the arithmetic logic used for memory allocation sizing. For applications that cannot be updated instantly due to dependency constraints, implementing strict input validation is essential. This involves sanitizing any user-supplied regular expression patterns to ensure they do not contain constructs known to trigger complex internal calculations within PCRE2. Additionally, deploying runtime protection mechanisms such as Address Space Layout Randomization and heap hardening techniques can help mitigate the impact of successful exploitation attempts by making memory corruption harder to exploit reliably.