CVE-2026-88370 in Applications
Summary
by MITRE • 09/24/2026
libconfini 1.16.4 contains a heap out-of-bounds write condition involving the bundled load_ini_buffer.h utility and strip_ini_cache(). The bundled utility allocates exactly ini_length bytes, while strip_ini_cache() unconditionally writes a NUL terminator at ini_source[ini_length], requiring an additional writable byte. Applications using the bundled allocation pattern can trigger deterministic heap memory corruption when processing any non-empty INI input, resulting in denial of service.
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Analysis
by VulDB Data Team • 09/24/2026
The vulnerability identified in libconfini version 1.16.4 represents a critical heap-based buffer overflow stemming from an off-by-one error within the library's configuration file parsing utilities. Specifically, the flaw resides in the interaction between the bundled load_ini_buffer.h utility and the strip_ini_cache function. The root cause is a failure to account for string termination requirements during memory allocation. When processing INI input files, the application allocates a buffer of exactly ini_length bytes based on the size of the source data. However, the subsequent call to strip_ini_cache performs an unconditional write operation that places a NUL terminator at the index corresponding to ini_source[ini_length]. In C-style string handling, this position is immediately outside the bounds of the allocated memory region, which spans from index zero to index ini_length minus one. This discrepancy creates a classic off-by-one heap overflow condition where data is written into adjacent memory structures rather than being contained within the intended buffer boundaries.
From an operational perspective, this vulnerability allows for deterministic heap memory corruption whenever any non-empty INI input file is processed by applications utilizing the bundled allocation pattern. Because the write operation occurs at a fixed offset relative to the allocated size, the exploitability of this flaw does not rely on complex payload construction or specific edge cases regarding data content length beyond being greater than zero. The immediate consequence is memory corruption that can lead to application crashes, resulting in a denial of service for any system relying on libconfini for configuration management. In more severe scenarios where heap metadata is overwritten, this vulnerability could potentially be leveraged by an attacker to achieve arbitrary code execution or privilege escalation, although the primary documented impact remains stability and availability degradation due to segmentation faults or abort signals triggered by memory protection mechanisms detecting the invalid write operation.
This issue aligns with Common Weakness Enumeration standard CWE-120, which classifies buffer copies without checking size limits as a category of out-of-bounds writes. Furthermore, it reflects CWE-789, describing memory allocation that is too small for its intended purpose due to integer overflows or logical errors in calculation. The attack vector typically involves supplying crafted INI configuration files through any interface where user-controlled input can influence the ini_length variable prior to buffer allocation. This could include web applications accepting file uploads, desktop software with open-file dialogs, or backend services parsing local configuration overrides provided by users or other system components.
Mitigation strategies should prioritize immediate patching of libconfini to a version that corrects this allocation logic. Developers must ensure that memory allocations for string buffers explicitly account for the null terminator byte when using functions like malloc or calloc based on strlen results. If upgrading is not immediately feasible, temporary workarounds involve validating input lengths and ensuring that any custom wrappers around these library calls allocate at least one additional byte beyond the measured content length. Additionally, implementing strict bounds checking in application code before invoking strip_ini_cache can prevent the out-of-bounds write from occurring if the underlying library version cannot be updated instantly. Security teams should also monitor for signs of heap corruption or unexpected process terminations associated with configuration file processing as an indicator of potential exploitation attempts against unpatched systems.