CVE-2019-16162 in Onigmo
Summary
by MITRE
Onigmo through 6.2.0 has an out-of-bounds read in parse_char_class because of missing codepoint validation in regenc.c.
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Analysis
by VulDB Data Team • 12/18/2023
The vulnerability identified as CVE-2019-16162 affects the Onigmo regular expression engine version 6.2.0 and earlier, presenting a critical out-of-bounds read condition that stems from inadequate codepoint validation within the regenc.c source file. This flaw manifests during the parsing of character classes through the parse_char_class function, where the engine fails to properly validate Unicode codepoint values before processing them. The absence of proper validation allows maliciously crafted regular expressions to trigger memory access violations that could potentially lead to information disclosure or system instability.
The technical root cause of this vulnerability resides in the insufficient input sanitization within the Unicode encoding handling component of Onigmo. When processing character class patterns, the parser does not validate whether the codepoint values fall within acceptable ranges or conform to proper Unicode standards. This missing validation creates a scenario where an attacker can construct regular expressions containing invalid or malformed codepoint sequences that cause the parser to read memory beyond the allocated buffer boundaries. The vulnerability specifically impacts the regenc.c file which handles encoding operations, making it a critical component in the attack vector.
This out-of-bounds read vulnerability presents significant operational risks to systems that rely on Onigmo for regular expression processing. Attackers could exploit this weakness by crafting malicious regular expressions that trigger the vulnerable code path, potentially leading to memory corruption, information leakage, or denial of service conditions. The impact extends across various applications that utilize Onigmo, including web servers, database systems, and security tools that depend on robust regular expression engines for pattern matching operations. Systems processing untrusted input through regular expressions become particularly vulnerable to this class of attack.
The vulnerability aligns with CWE-129, which addresses improper validation of input boundaries, and demonstrates characteristics consistent with ATT&CK technique T1059.007 for application layer command injection. Organizations should prioritize immediate patching of affected systems to address this vulnerability, as the out-of-bounds read could potentially be leveraged for more sophisticated attacks. The recommended mitigation strategy involves upgrading to Onigmo version 6.2.1 or later, which includes the necessary codepoint validation fixes. Additionally, implementing proper input validation and sanitization measures at the application level can provide additional defense-in-depth against similar vulnerabilities in other components. Security monitoring should be enhanced to detect unusual regular expression patterns that might indicate exploitation attempts targeting this vulnerability.