CVE-2026-102514 in PeaZip
Summary
by MITRE • 10/02/2026
Out-of-bounds Write (CWE-787) in the PEA archive extraction routine (pea.pas, unpea_procedure) of the first-party pea component in PeaZip 11.2.0 and earlier allows an attacker who convinces a victim to open or extract a crafted .pea archive to execute arbitrary code as the user running PeaZip. While decompressing a PCOMPRESS1 stream, the 32-bit compressed-block-size field of the first block (compsize) is read directly from the archive and used without validation as the length of a blockread into the fixed-size global buffers wbuf1/wbuf2 (1,114,112 bytes) and as the bound of the subsequent copy loop. The existing check "compsize > WBUFSIZE" is applied only to the size of each following block, so the first block escapes it; the same unvalidated value is also used to index wbuf1[compsize], an out-of-bounds read at an attacker-chosen offset. The copy loop additionally copies the requested length instead of the number of bytes actually read, and terminates on equality rather than on an upper bound. Because the project is built without range checking and no archive password, integrity tag or non-default configuration is required, the overflow overwrites adjacent global data; code execution was demonstrated by two independent researchers against the official Linux x86-64 and Windows x64 builds, and the denial-of-service and memory-corruption primitive is cross-platform (Windows, macOS, Linux, BSD).
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Analysis
by VulDB Data Team • 10/02/2026
The vulnerability identified in PeaZip versions 11.2.0 and earlier represents a critical out-of-bounds write flaw within the PEA archive extraction routine located in pea.pas under the unpea_procedure function. This security defect allows an attacker to achieve arbitrary code execution by convincing a victim to open or extract a maliciously crafted .pea archive. The root cause lies in the improper validation of input data during the decompression process, specifically when handling PCOMPRESS1 streams. When processing such archives, the application reads the compressed-block-size field from the first block directly into a variable named compsize without performing adequate bounds checking against the available buffer space. This value is then used as both the length parameter for reading data into fixed-size global buffers and as an index limit in subsequent operations, creating multiple vectors for memory corruption.
The technical mechanism of exploitation involves two distinct but related issues within the same code path. First, while there exists a check to ensure that compsize does not exceed WBUFSIZE, this validation is incorrectly applied only to blocks following the first one. Consequently, the size specified in the initial block escapes this safety measure entirely. The application proceeds to use this unvalidated compsize value as the upper bound for copying data into global buffers wbuf1 and wbuf2, which have a fixed capacity of 1,114,112 bytes. If an attacker crafts an archive where the first block's size exceeds this limit, the copy operation will write beyond the allocated memory boundaries. Additionally, the code performs an out-of-bounds read by indexing into wbuf1 using compsize as the offset, further indicating a lack of rigorous input sanitization before accessing array elements based on untrusted external data.
The operational impact of this vulnerability is severe due to the nature of the resulting memory corruption primitive. The copy loop in question copies the requested length rather than verifying the actual number of bytes successfully read from the archive stream. Furthermore, the termination condition for the loop relies on equality with a counter that may not accurately reflect safe boundaries because it terminates based on an unchecked upper bound rather than a validated limit. Because the project is compiled without range checking enabled and does not require specific integrity tags or non-default configurations to trigger this flaw, the vulnerability is highly exploitable across multiple platforms including Windows x64, Linux x86-64, macOS, and BSD systems. Successful exploitation allows an attacker to overwrite adjacent global data structures in memory, which can be manipulated to hijack control flow and execute arbitrary code with the privileges of the user running PeaZip.
This vulnerability aligns with CWE-787 (Out-of-bounds Write) as it involves writing data beyond the intended buffer boundary due to insufficient validation of array indices or lengths. From a threat modeling perspective, this flaw facilitates remote code execution through social engineering tactics such as lure files, mapping closely to MITRE ATT&CK techniques related to initial access and defense evasion via crafted archives. To mitigate this risk, users should immediately update PeaZip to the latest patched version where proper bounds checking is enforced for all archive blocks regardless of their position in the stream. Developers must implement strict validation that compares input sizes against buffer limits before any memory allocation or copy operations occur. Additionally enabling compiler-level range checks and implementing integrity verification mechanisms can provide defense-in-depth layers that prevent exploitation even if logical errors persist within the extraction logic.