CVE-2005-4077 in cURL
Summary
by MITRE
Multiple off-by-one errors in the cURL library (libcurl) 7.11.2 through 7.15.0 allow local users to trigger a buffer overflow and cause a denial of service or bypass PHP security restrictions via certain URLs that (1) are malformed in a way that prevents a terminating null byte from being added to either a hostname or path buffer, or (2) contain a "?" separator in the hostname portion, which causes a "/" to be prepended to the resulting string.
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Analysis
by VulDB Data Team • 06/22/2025
The CVE-2005-4077 vulnerability represents a critical buffer overflow issue within the cURL library version 7.11.2 through 7.15.0, affecting a fundamental component widely used across numerous applications and systems for handling HTTP and other protocol communications. This vulnerability stems from multiple off-by-one errors that occur during URL parsing and buffer management, creating exploitable conditions that can lead to system instability and potential security bypasses. The cURL library serves as a core dependency for many web applications, scripting languages, and system tools, making this vulnerability particularly dangerous as it can affect a broad spectrum of software environments.
The technical flaw manifests through two distinct but related conditions that exploit improper buffer handling during URL processing. The first condition occurs when malformed URLs prevent a terminating null byte from being properly added to either hostname or path buffers, creating situations where buffer boundaries are exceeded during string operations. The second condition involves URLs containing a "?" separator within the hostname portion, which causes a "/" character to be prepended to the resulting string, thereby corrupting buffer boundaries and potentially leading to memory corruption. These off-by-one errors fall under CWE-121, which specifically addresses stack-based buffer overflow conditions, and represent a classic example of improper input validation leading to memory safety issues. The vulnerability directly relates to CWE-129, which covers insufficient boundary checking, and CWE-787, which addresses out-of-bounds write conditions.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable more sophisticated attacks. Local users can exploit these buffer overflows to cause application crashes, leading to denial of service conditions that disrupt legitimate system operations. More critically, the vulnerability can be leveraged to bypass PHP security restrictions, allowing attackers to potentially execute unauthorized operations or access restricted resources. The implications are particularly severe in web server environments where cURL is used for fetching remote content, as malicious URLs could be crafted to exploit these conditions and compromise server integrity. This vulnerability directly aligns with ATT&CK technique T1059, which covers command and scripting interpreter usage, and T1499, covering endpoint denial of service, while also supporting T1566, which involves malicious file execution through compromised applications.
Mitigation strategies for CVE-2005-4077 require immediate patching of affected cURL library versions, with organizations prioritizing updates to versions beyond 7.15.0 where these buffer overflow conditions have been resolved. System administrators should implement comprehensive monitoring for malformed URL patterns and establish robust input validation mechanisms to prevent exploitation attempts. Security teams should consider implementing network-based intrusion detection systems that can identify suspicious URL patterns associated with this vulnerability, particularly in web applications that utilize cURL for remote content retrieval. Additionally, organizations should conduct thorough vulnerability assessments to identify all systems using affected cURL versions and ensure proper patch management procedures are in place. The remediation process should include not only updating the cURL library but also reviewing application code that relies on this library to ensure proper error handling and input validation mechanisms are implemented to prevent similar vulnerabilities from emerging in custom implementations.