CVE-2012-0036 in cURL
Summary
by MITRE
curl and libcurl 7.2x before 7.24.0 do not properly consider special characters during extraction of a pathname from a URL, which allows remote attackers to conduct data-injection attacks via a crafted URL, as demonstrated by a CRLF injection attack on the (1) IMAP, (2) POP3, or (3) SMTP protocol.
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Analysis
by VulDB Data Team • 03/20/2021
The vulnerability identified as CVE-2012-0036 represents a critical path traversal and injection flaw affecting curl and libcurl versions prior to 7.24.0. This issue stems from inadequate handling of special characters during URL pathname extraction, creating a pathway for malicious actors to inject harmful data into protocol communications. The flaw specifically impacts three major email protocols including IMAP, POP3, and SMTP, making it particularly dangerous for email server communications and client applications that rely on these protocols for data transmission.
The technical root cause of this vulnerability lies in the improper sanitization of URL components during the parsing process. When curl or libcurl processes a URL containing special characters, the software fails to correctly handle sequences that could be interpreted as control characters or protocol delimiters. This processing error allows attackers to craft malicious URLs that contain carriage return line feed sequences or other special characters that get inadvertently incorporated into the pathname extraction process. The vulnerability specifically enables CRLF injection attacks, where attackers can inject malicious control sequences that manipulate how the protocol handles data transmission and processing.
The operational impact of this vulnerability extends beyond simple data injection, as it can lead to severe consequences in email server communications and client applications. Attackers can exploit this flaw to inject commands or manipulate protocol behavior, potentially leading to unauthorized access, data leakage, or disruption of email services. The vulnerability is particularly concerning because it affects widely used email protocols that form the backbone of business communications. When exploited against IMAP, POP3, or SMTP servers, the injection attacks can compromise the integrity of email communications and potentially allow for more sophisticated attacks such as man-in-the-middle scenarios or unauthorized data access.
The implications of this vulnerability align with CWE-117, which addresses improper output neutralization for logs, and also relates to ATT&CK technique T1071.004 for application layer protocol manipulation. Organizations using affected versions of curl or libcurl in email client applications, mail servers, or any system that processes email protocols through these libraries are at risk of exploitation. The vulnerability demonstrates the critical importance of proper input validation and sanitization in network communication libraries, particularly those handling protocol-specific data processing. Security practitioners should prioritize updating affected systems to version 7.24.0 or later, as this release includes the necessary patches to properly handle special characters during URL pathname extraction and prevent the injection attacks that this vulnerability enables.
This vulnerability highlights the broader challenge of secure URL handling in network libraries and the potential for seemingly benign parsing operations to create security weaknesses. The flaw represents a classic example of how insufficient input validation in core networking libraries can create attack vectors that span multiple protocols and affect critical infrastructure components. Organizations should implement comprehensive patch management procedures to address this vulnerability promptly, as the attack surface extends to any system that relies on curl or libcurl for email protocol communications and network data processing operations.