CVE-2026-92627 in HDF5
Summary
by MITRE • 09/16/2026
A heap-use-after-free vulnerability exists in H5T__conv_f_f() in src/H5Tconv.c in HDF5 before 2.3.0. When converting a compound datatype containing floating-point members during a dataset read, a temporary buffer allocated with calloc() is freed and subsequently read from within the same conversion routine. An attacker who can supply a crafted HDF5 file containing a specially constructed compound datatype can trigger the use-after-free when the file is parsed by an application that reads the affected dataset, such as h5dump. This can result in a crash and, depending on heap layout and allocator behavior, may be exploitable for further memory corruption up to remote code execution.
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Analysis
by VulDB Data Team • 09/16/2026
The vulnerability identified in HDF5 versions prior to 2.3.0 represents a critical heap-use-after-free condition located within the H5T__conv_f_f() function found in src/H5Tconv.c. This specific component is responsible for handling data type conversions, particularly when dealing with compound datatypes that include floating-point members during dataset read operations. The core technical flaw stems from improper memory management logic where a temporary buffer allocated via calloc() is prematurely freed before the conversion routine has completed its necessary read operations on that same memory region. This sequence violation means that once the memory block is returned to the heap allocator, any subsequent access attempts by the application result in reading from deallocated memory space, which constitutes an undefined behavior according to standard C programming practices and poses significant security risks.
From a technical perspective, this vulnerability allows for potential exploitation through crafted HDF5 files containing specially constructed compound datatypes. When an application such as h5dump or any other software utilizing the vulnerable HDF5 library parses these maliciously formatted files, it triggers the use-after-free condition during the dataset read process. The exploitability of this flaw depends heavily on heap layout and allocator behavior within the target environment. In many modern memory allocators, freed chunks are not immediately zeroed out but may remain in a state where their contents can be accessed if referenced by dangling pointers. This characteristic enables attackers to potentially control or influence the data read from these freed regions, leading to arbitrary code execution scenarios under specific conditions.
The operational impact of this vulnerability is severe, ranging from denial-of-service attacks through application crashes to more sophisticated remote code execution exploits. An attacker who can supply a crafted HDF5 file to a victim system running an affected version of HDF5 can trigger the crash or exploit the memory corruption for further malicious activities. The ability to achieve arbitrary code execution via heap-based vulnerabilities is particularly concerning because it bypasses many traditional security controls that rely on preventing stack overflows. Successful exploitation could allow unauthorized access to sensitive data, modification of application state, or complete compromise of the underlying system depending on the privileges held by the vulnerable process.
This vulnerability aligns with CWE-416, which describes Use After Free errors where a pointer is used after it has been freed leading to unpredictable behavior and potential security breaches. Additionally, from an adversarial tactics perspective, this flaw can be leveraged within ATT&CK framework techniques related to initial access via crafted files such as T1203 or exploitation for privilege escalation if the application runs with elevated permissions. The mismanagement of dynamic memory allocation highlights a critical gap in input validation and lifecycle management of allocated resources within the HDF5 library's conversion routines.
To mitigate this risk, organizations must immediately upgrade to HDF version 2.3.0 or later where the issue has been resolved by correcting the timing of buffer deallocation relative to its usage. Until an update is applied, defensive measures should include restricting the ability of untrusted users to upload or process HDF5 files within critical systems and employing sandboxing techniques to limit the impact of potential crashes or exploits. Input validation mechanisms that inspect compound datatype structures before processing can also help detect malformed inputs early in the pipeline. Regular security audits focusing on memory management practices in C-based libraries are essential for preventing similar vulnerabilities from being introduced into software ecosystems reliant on robust data handling capabilities.