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).
Upgrade to PeaZip 11.3.0 or higher, which validates the size of the first compressed block (commit 90ddbae), copies the number of bytes actually read, and stops the block-reading loop when the address exceeds the expected value.