CVE-2026-44722

### Impact A Python operator precedence bug in pyzipper/zipfile_aes.py caused the AE-2 format to never be automatically selected during encryption, regardless of file size or compression type. As a result, all encrypted entries are written in AE-1 format unless AE-2 is explicitly forced by the caller. AE-1 stores the plaintext CRC32 checksum unencrypted in the ZIP header. During investigation of this issue, it was also found that when writing to an unseekable zip archive, the CRC32 value was always written to the datadescripter section. The AES encryption itself is not broken. An attacker who possesses the archive can read the CRC32 from the header without decrypting anything, then brute-force candidate plaintexts by computing CRC32(candidate) and comparing against the stored value. In practice, this attack is feasible today only against small or low-entropy files, as CRC32 exhaustion across a large plaintext space is computationally prohibitive on current hardware. Files with high-entropy or large content are not practically at risk under current computing constraints. Without this bug, pyzipper would have removed the CRC32 value for any file with content of less than 20 bytes uncompressed. ### Patches Upgrade to pyzipper 0.4.0 that changes the default behaviour of pyzipper to always use the AE-2 format and exclude the CRC32 values, unless instructed to do otherwise. If rewriting the zip archive to remove the CRC values for small files, the entire zip archive should be recreated to avoid the original local file header with the CRC included remaining in the zip file in a detached state. ## Credit Thanks to Lucas Lavarello from Kulkan Security for identifying this issue. ### References https://www.winzip.com/en/support/aes-encryption/#CRC https://www.winzip.com/en/support/aes-encryption/#crc-faq

### Impact A Python operator precedence bug in pyzipper/zipfile_aes.py caused the AE-2 format to never be automatically selected during encryption, regardless of file size or compression type. As a result, all encrypted entries are written in AE-1 format unless AE-2 is explicitly forced by the caller. AE-1 stores the plaintext CRC32 checksum unencrypted in the ZIP header. During investigation of this issue, it was also found that when writing to an unseekable zip archive, the CRC32 value was always written to the datadescripter section. The AES encryption itself is not broken. An attacker who possesses the archive can read the CRC32 from the header without decrypting anything, then brute-force candidate plaintexts by computing CRC32(candidate) and comparing against the stored value. In practice, this attack is feasible today only against small or low-entropy files, as CRC32 exhaustion across a large plaintext space is computationally prohibitive on current hardware. Files with high-entropy or large content are not practically at risk under current computing constraints. Without this bug, pyzipper would have removed the CRC32 value for any file with content of less than 20 bytes uncompressed. ### Patches Upgrade to pyzipper 0.4.0 that changes the default behaviour of pyzipper to always use the AE-2 format and exclude the CRC32 values, unless instructed to do otherwise. If rewriting the zip archive to remove the CRC values for small files, the entire zip archive should be recreated to avoid the original local file header with the CRC included remaining in the zip file in a detached state. ## Credit Thanks to Lucas Lavarello from Kulkan Security for identifying this issue. ### References https://www.winzip.com/en/support/aes-encryption/#CRC https://www.winzip.com/en/support/aes-encryption/#crc-faq

pyzipper es un reemplazo para el módulo zipfile de Python que puede leer y escribir archivos zip cifrados con AES. Antes de la versión 0.4.0, un error de precedencia de operadores de Python en pyzipper/zipfile_aes.py hizo que el formato AE-2 nunca se seleccionara automáticamente durante el cifrado, lo que provocó que las entradas cifradas se escribieran en formato AE-1 y exponiendo la suma de verificación CRC32 en texto plano en la cabecera ZIP y, para archivos zip no buscables, en la sección del descriptor de datos, permitiendo a un atacante que posee el archivo forzar por fuerza bruta posibles textos planos para archivos pequeños o de baja entropía comparando los valores CRC32. Este problema está corregido en la versión 0.4.0.