CVE-2018-19198 in uriparser
Summary
by MITRE
An issue was discovered in uriparser before 0.9.0. UriQuery.c allows an out-of-bounds write via a uriComposeQuery* or uriComposeQueryEx* function because the '&' character is mishandled in certain contexts.
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Analysis
by VulDB Data Team • 06/05/2023
The vulnerability identified as CVE-2018-19198 resides within the uriparser library version 0.8.4 and earlier, representing a critical out-of-bounds write flaw that affects applications relying on URI composition functionality. This issue specifically impacts the uriQuery.c component of the library, which handles query string processing and composition operations. The vulnerability manifests when applications utilize the uriComposeQuery or uriComposeQueryEx functions, which are designed to construct query strings from parsed URI components. The flaw occurs due to improper handling of the ampersand character '&' within specific contextual scenarios, creating a condition where memory beyond the allocated buffer boundaries can be written to, potentially leading to arbitrary code execution or system instability.
The technical root cause of this vulnerability stems from inadequate bounds checking during query string composition operations. When the uriComposeQuery* functions process query parameters, they fail to properly account for the '&' character's role as a parameter separator in URL query strings. This oversight results in buffer overflow conditions where the library attempts to write data beyond the intended memory allocation. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, though it manifests as an out-of-bounds write due to the nature of how the library manages memory allocation for query string construction. The improper handling of the '&' character creates a scenario where the library's internal buffer management logic fails to account for the additional character required to properly separate query parameters, leading to memory corruption that can be exploited by attackers.
The operational impact of CVE-2018-19198 extends across numerous applications and systems that depend on uriparser for URI processing, particularly those handling user-provided URLs or web requests. Applications affected include web browsers, web servers, proxy servers, and any software that processes or constructs URI query strings from user input. The vulnerability can be exploited through crafted URLs that contain specially formatted query parameters, potentially allowing remote attackers to execute arbitrary code on vulnerable systems or cause denial of service conditions. Attackers can leverage this flaw to inject malicious data into memory locations, potentially leading to privilege escalation or complete system compromise, depending on the execution context of the affected application. The vulnerability is particularly dangerous in web applications where user input is processed without proper sanitization, as it can be triggered through simple URL manipulation.
Mitigation strategies for CVE-2018-19198 involve immediate upgrading to uriparser version 0.9.0 or later, which contains the necessary fixes for the buffer overflow vulnerability. System administrators should conduct comprehensive vulnerability assessments to identify all applications using affected versions of the library and prioritize their remediation. Additionally, implementing input validation and sanitization measures can provide defense-in-depth protection, particularly for applications that cannot be immediately upgraded. The fix implemented in version 0.9.0 addresses the core issue by properly handling the '&' character during query string composition and implementing robust bounds checking mechanisms. Organizations should also consider applying runtime protections such as address space layout randomization and stack canaries to reduce the exploitability of similar vulnerabilities. The ATT&CK framework categorizes this vulnerability under T1059.007 for command and scripting interpreter and T1190 for exploit public-facing application, as it represents a common attack vector through web application interfaces. Regular security audits and dependency management practices should be implemented to prevent similar vulnerabilities from emerging in other components of the software supply chain.