CVE-2017-9224 in Oniguruma
Summary
by MITRE
An issue was discovered in Oniguruma 6.2.0, as used in Oniguruma-mod in Ruby through 2.4.1 and mbstring in PHP through 7.1.5. A stack out-of-bounds read occurs in match_at() during regular expression searching. A logical error involving order of validation and access in match_at() could result in an out-of-bounds read from a stack buffer.
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Analysis
by VulDB Data Team • 12/07/2022
The vulnerability identified as CVE-2017-9224 represents a critical stack out-of-bounds read condition within the Oniguruma regular expression engine version 6.2.0. This flaw affects multiple programming environments including Ruby versions through 2.4.1 via the Oniguruma-mod extension and PHP versions through 7.1.5 through the mbstring extension. The vulnerability stems from a fundamental logical error in the match_at() function where validation and memory access operations are improperly ordered, creating a window where memory can be accessed beyond its allocated boundaries.
The technical implementation of this vulnerability occurs within the match_at() function of the Oniguruma library, where a sequence of operations fails to properly validate buffer boundaries before accessing memory locations. This logical flaw creates a scenario where an attacker can craft malicious regular expressions that trigger an out-of-bounds read condition when the regular expression engine processes these inputs. The stack buffer overflow occurs because the validation checks happen after the memory access operations, allowing the program to read from memory locations that may contain sensitive data or be uninitialized. This type of vulnerability falls under CWE-129, which specifically addresses improper validation of array indices, and more broadly relates to CWE-787, which covers out-of-bounds write operations. The vulnerability represents a classic case of improper input validation where the order of operations creates an exploitable condition.
The operational impact of this vulnerability extends across multiple software ecosystems that rely on regular expression processing, particularly affecting web applications, text processing utilities, and systems that handle untrusted input through regular expression operations. When exploited, the out-of-bounds read can potentially expose sensitive information from the program's memory space, including stack contents, which might contain cryptographic keys, session tokens, or other confidential data. The vulnerability is particularly concerning because regular expressions are commonly used in input validation, data parsing, and text processing functions across numerous applications, making the attack surface quite broad. From an adversarial perspective, this vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter, specifically targeting the execution of regular expressions as a means of information disclosure. The vulnerability can be exploited through crafted regular expressions that, when processed by vulnerable applications, trigger the out-of-bounds read condition and potentially lead to information leakage or further exploitation attempts.
Mitigation strategies for CVE-2017-9224 involve immediate patching of affected software versions to utilize fixed versions of the Oniguruma library, which addresses the logical error in the match_at() function by reordering validation and access operations. System administrators should prioritize updating Ruby installations to versions 2.4.2 or later and PHP installations to versions 7.1.6 or later, which include the necessary fixes. Additionally, implementing input validation measures that limit the complexity and length of regular expressions processed by applications can help reduce the risk of exploitation. Organizations should also consider implementing proper memory access controls and using address sanitization tools during development and testing phases to detect similar vulnerabilities. The remediation process should include comprehensive testing of applications to ensure that patched versions properly handle regular expressions without triggering the out-of-bounds read condition. Security monitoring should be enhanced to detect potential exploitation attempts through unusual regular expression patterns or unexpected memory access behaviors in applications that utilize vulnerable libraries.