CVE-2026-44722CWE-480

pyzipper: Encryption bypass for small files encrypted with pyzipper

Medium · published July 17, 2026

CVSS v3.1
6.2
EPSS
0%
Percentile
1.8
In the wild
Unconfirmed
What it is

pyzipper is a replacement for Python's zipfile that can read and write AES encrypted zip files. Prior to 0.4.0, a Python operator precedence bug in pyzipper/zipfile_aes.py caused the AE-2 format to never be automatically selected during encryption, causing encrypted entries to be written in AE-1 format and exposing the plaintext CRC32 checksum in the ZIP header and, for unseekable zip archives, in the datadescripter section, allowing an attacker who possesses the archive to brute-force candidate plaintexts for small or low-entropy files by comparing CRC32 values. This issue is fixed in version 0.4.0.

The record
Technical detail
CVSS v3.1
6.2 · MEDIUM
Vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
CVSS v4.0
Not supplied
EPSS
0.00116 · 1.8th percentile
Weakness
CWE-480 · Use of Incorrect Operator
Published
2026-07-17T16:42Z
EPSS history
Timeline
  • 17 JUL 16:42Z
    pyzipper: Encryption bypass for small files encrypted with pyzipper
    cvelistv5