CVE-2023-32001 in cURL
Summary
by MITRE • 07/27/2023
libcurl can be told to save cookie, HSTS and/or alt-svc data to files. When doing this, it called `stat()` followed by `fopen()` in a way that made it vulnerable to a TOCTOU race condition problem. By exploiting this flaw, an attacker could trick the victim to create or overwrite protected files holding this data in ways it was not intended to.
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Analysis
by VulDB Data Team • 08/15/2023
The vulnerability identified as CVE-2023-32001 resides within the libcurl library, a widely used open source software component that facilitates data transfer operations across numerous applications and systems. This library implements cookie management, HSTS (HTTP Strict Transport Security), and alt-svc (Alternative Services) functionality, all of which rely on persistent file storage mechanisms. The flaw manifests when applications configure libcurl to store this security-sensitive data to disk, creating a potential attack surface that could compromise system integrity and security posture. The vulnerability specifically affects the file creation and access patterns employed by libcurl during the persistence of security data, creating opportunities for malicious actors to manipulate the system state.
The technical implementation of this vulnerability stems from a classic Time-of-Check to Time-of-Use race condition pattern that directly aligns with CWE-367. The flaw occurs when libcurl performs a sequence of operations involving the stat() system call to check file attributes followed by fopen() to open or create files for data persistence. During this window between the stat() check and the actual file operation, an attacker can manipulate the filesystem state by replacing the target file with a symbolic link or by changing directory permissions. This race condition creates a scenario where the application's security checks pass successfully, but the subsequent file operations target different files than originally intended. The vulnerability is particularly concerning because it operates at the file system level, allowing attackers to potentially overwrite critical system files or create malicious files with elevated privileges.
The operational impact of CVE-2023-32001 extends beyond simple file manipulation, as it can lead to privilege escalation and persistent security breaches within affected systems. When applications using libcurl store security data such as cookies, HSTS entries, or alt-svc records, attackers who successfully exploit this race condition could potentially overwrite system files with malicious content, manipulate security policies, or establish backdoor access paths. The vulnerability affects any application that relies on libcurl for HTTP operations and has configured it to persist security data to disk. This includes web browsers, network monitoring tools, automated scripts, and enterprise applications that utilize libcurl as their underlying HTTP transfer library. The implications are particularly severe in environments where applications run with elevated privileges or where the affected files are located in system directories with restricted access controls.
Mitigation strategies for CVE-2023-32001 require immediate attention from system administrators and application developers who utilize libcurl. The most effective approach involves updating to the patched version of libcurl that eliminates the race condition by implementing atomic file creation operations or by using file locking mechanisms to prevent concurrent access during critical file operations. Organizations should conduct comprehensive vulnerability assessments to identify all applications that utilize libcurl and have configured security data persistence. Additionally, implementing proper file system permissions and monitoring for unauthorized file modifications can help detect potential exploitation attempts. Security teams should also consider implementing application whitelisting policies that restrict file system access for applications that do not require direct file I/O operations for security data management. The vulnerability demonstrates the importance of following secure coding practices and adheres to ATT&CK technique T1059.007 for privilege escalation through file system manipulation. Regular security audits and patch management procedures should be enhanced to address similar race condition vulnerabilities in other system components, as these flaws often represent significant attack vectors in modern computing environments.