CVE-2026-44722: Pyzipper Pyzipper Has An Encryption Bypass Vulnerability

MODERATE
Advisory Identifier: GHSA-crqm-m339-7m2p
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CVSS 6.2
CWE-480
Published
Advisory Summary

CVE-2026-44722 is a MODERATE (CVSS 6.2) pyzipper has an encryption bypass vulnerability (CWE-480: Use of Incorrect Operator) affecting Pyzipper libraries in the PyPI ecosystem. The issue involves pyzipper has an encryption bypass for small files encrypted using it. Remediation is available by upgrading affected packages to version 0.4.0.

CVE-2026-44722 at a Glance

CVE Identifier CVE-2026-44722
GHSA Identifier GHSA-crqm-m339-7m2p
Severity MODERATE
CVSS v3.1 Base Score 6.2
CWE Classification CWE-480: Use of Incorrect Operator
Affected Product Pyzipper
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 6.2

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).

Attack Vector Local (AV:L)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2026-44722

To remediate this vulnerability, upgrade all affected Pyzipper dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

pyzipper fixed: 0.4.0 
pip install pyzipper>=0.4.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show pyzipper

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-44722, inspect your installed packages using pip:

pip show pyzipper

Analyze the terminal output to locate any version of Pyzipper in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.4.0), your application is affected.

Note: The pip show pyzipper command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-480: Use of Incorrect Operator, where the product accidentally uses the wrong operator, which changes the logic in security-relevant ways. In Pyzipper, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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

CVE-2026-44722 Affected Pyzipper Versions

1 component(s)
Fixed Versions:
0.4.0
Product / Package Ecosystem Affected Versions Fixed Version
pyzipper
pypi/pyzipper
PyPI
< 0.4.0
0.4.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/danifus/pyzipper/security/advisories/GHSA-crqm-m339-7m2p
Pyzipper Source Repository REPOSITORY
https://github.com/danifus/pyzipper
Pyzipper Release RELEASE
https://github.com/danifus/pyzipper/releases/tag/v0.4.0

Frequently Asked Questions

What is CVE-2026-44722?
CVE-2026-44722 is a security vulnerability in Pyzipper involving pyzipper has an encryption bypass for small files encrypted using it under CWE-480: Use of Incorrect Operator.
Which Pyzipper versions are affected?
Affected versions include releases prior to 0.4.0 across affected packages: pyzipper.
What version fixes CVE-2026-44722?
Upgrading to 0.4.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is pyzipper affected?
Yes, pyzipper is affected in releases prior to 0.4.0. Upgrade your dependency to 0.4.0 or later.
What is the CVSS score of CVE-2026-44722?
CVE-2026-44722 has a CVSS v3.1 base score of 6.2 (MODERATE) with vector string CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
What CWE is associated with CVE-2026-44722?
CVE-2026-44722 is classified under CWE-480: Use of Incorrect Operator (The product accidentally uses the wrong operator, which changes the logic in security-relevant ways.).
How can I check PyPI dependencies for CVE-2026-44722?
Run the dependency tree command: 'pip show pyzipper'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-crqm-m339-7m2p",
  "modified" : "2026-05-14T16:17:01Z",
  "published" : "2026-05-14T16:17:01Z",
  "aliases" : [ "CVE-2026-44722" ],
  "summary" : "pyzipper has an encryption bypass for small files encrypted using it",
  "details" : "### Impact\nA 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.\n\nThe 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.\n\n### Patches\nUpgrade 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.\n\nIf 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.\n\n## Credit\nThanks to Lucas Lavarello from Kulkan Security for identifying this issue.\n\n### References\nhttps://www.winzip.com/en/support/aes-encryption/#CRC\nhttps://www.winzip.com/en/support/aes-encryption/#crc-faq",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"
  } ],
  "affected" : [ {
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      "name" : "pyzipper"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
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      }, {
        "fixed" : "0.4.0"
      } ]
    } ]
  } ],
  "references" : [ {
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  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/danifus/pyzipper"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/danifus/pyzipper/releases/tag/v0.4.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-480" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-14T16:17:01Z",
    "nvd_published_at" : null
  }
}