How severe is CVE-2026-44722?

CVE-2026-44722 has a CVSS score of 6.2/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2026-44722?

CVE-2026-44722 affects the following packages: pyzipper (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-44722?

Update pyzipper to 0.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44722 is resolved across your whole dependency graph.

How do I detect CVE-2026-44722 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pyzipper, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-44722 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-44722 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-44722 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-44722?

CVE-2026-44722 has an EPSS (Exploit Prediction Scoring System) score of 0.1%, placing it in the 1th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

When was CVE-2026-44722 published, and has it been updated?

CVE-2026-44722 was published on July 17, 2026 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍

🐍 PyPI

Not in CISA KEV

MEDIUM severity

CVE-2026-44722 — pyzipper

MEDIUMFix: danifus/pyzipper@93ce88e

CVE-2026-44722 is a medium-severity (CVSS 6.2) vulnerability in pyzipper. A fix is available for pyzipper — see the affected versions and patch details below.

pyzipper: Encryption bypass for small files encrypted with pyzipper

Also known asGHSA-crqm-m339-7m2pPYSEC-2026-3044

Published

Jul 17, 2026

Updated

Aug 12, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 26, 2026 · OSV.dev, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-44722.

EPSS Exploitation Probability

via FIRST.org ↗

0.1%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs1th percentile — riskier than 1% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-44722 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 379,842 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

🐍pyzipper

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

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

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`pyzipper`	all versions	0.4.0`pip install --upgrade 'pyzipper==0.4.0'`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pyzipper, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update pyzipper to 0.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44722 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### 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

O3 Security · Impact-Aware SCA

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