CVE-2018-15157 in libfsclfs
Summary
by MITRE
** DISPUTED ** The libfsclfs_block_read function in libfsclfs_block.c in libfsclfs before 2018-07-25 allows remote attackers to cause a heap-based buffer over-read via a crafted clfs file. NOTE: the vendor has disputed this as described in the GitHub issue comments.
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Analysis
by VulDB Data Team • 08/05/2024
The vulnerability identified as CVE-2018-15157 affects the libfsclfs library, specifically within the libfsclfs_block_read function located in libfsclfs_block.c. This flaw represents a heap-based buffer over-read condition that can be exploited by remote attackers through the manipulation of crafted clfs files. The issue was discovered in versions of libfsclfs prior to the 2018-07-25 release, indicating a window of potential exploitation that spans several months. The vulnerability's classification as a heap-based buffer over-read aligns with CWE-125, which describes out-of-bounds read conditions that can lead to information disclosure or system instability. The function's handling of clfs file structures appears to lack proper bounds checking mechanisms, allowing an attacker to craft malicious input that exceeds the allocated buffer boundaries.
The operational impact of this vulnerability extends beyond simple information disclosure, as heap-based buffer over-reads can potentially lead to more severe consequences including arbitrary code execution or system crashes. When a remote attacker successfully crafts a malicious clfs file, the libfsclfs_block_read function processes the malformed input without adequate validation, resulting in memory access beyond the intended buffer limits. This behavior creates opportunities for attackers to read sensitive data from adjacent memory locations, potentially exposing cryptographic keys, authentication tokens, or other confidential information stored in the heap memory. The remote exploitation aspect means that attackers do not require local access to the system, making this vulnerability particularly concerning for networked applications that process untrusted clfs file inputs.
From a threat modeling perspective, this vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as it could enable attackers to extract information that might be used to further compromise systems. The vulnerability's remote nature and the fact that it operates on file processing functions suggest that it could be exploited through various attack vectors including web applications, file sharing systems, or any service that accepts and processes clfs file inputs. The vendor's disputed status indicates that there may be disagreements regarding the severity or exploitability of the issue, though the underlying technical flaw in buffer handling remains a legitimate concern for systems that rely on this library. Organizations using libfsclfs should carefully evaluate their exposure and consider alternative implementations or patches even if the vendor disputes the vulnerability classification.
The technical flaw manifests in the insufficient validation of input parameters within the libfsclfs_block_read function, where the code fails to properly verify the size or content of clfs file structures before attempting to read data into allocated buffers. This lack of proper bounds checking creates a predictable pattern where attacker-controlled input can cause memory access violations that extend beyond the intended buffer boundaries. The heap-based nature of the vulnerability means that the affected memory regions are dynamically allocated, making the exploitation patterns more complex and potentially more dangerous than stack-based buffer overflows. The vulnerability's potential for information disclosure through heap reading could expose sensitive system information that might aid in subsequent attacks, including privilege escalation or lateral movement within compromised networks. Security practitioners should implement monitoring for unusual file processing patterns and consider input sanitization measures to prevent exploitation of this and similar buffer over-read conditions.