CVE-2021-33430: A Buffer Overflow vulnerability exists in NumPy 1.9.x in the PyArray_NewFromDescr_int function of ctors.c when

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MEDIUM 5.3UPGRADE

CVE-2021-33430 is a medium-severity flaw (CVSS 5.3) affecting numpy. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A Buffer Overflow vulnerability exists in NumPy 1.9.x in the PyArray_NewFromDescr_int function of ctors.c when specifying arrays of large dimensions (over 32) from Python code, which could let a malicious user cause a Denial of Service. NOTE: The vendor does not agree this is a vulneraility; In (very limited) circumstances a user may be able provoke the buffer overflow, the user is most likely already privileged to at least provoke denial of serv

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	Low
User interaction	None
EPSS exploit chance	1.2% (top 33%)
CISA exploited list	No
Weakness	CWE-120
Published	2021-12-17
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: numpy

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-12-17 19:15 UTCPublished CVE record published
2026-06-17 03:54 UTCUpdated Record last modified

numpy numpy UPGRADE

Affected: >= 1.9.0 and <= 1.9.3

Fixed in: newer than 1.9.3

Safe to downgrade to: a release before 1.9.0

1. Check installed version

apt-cache policy numpy || rpm -q numpy || numpy --version

2. UPGRADE to newer than 1.9.3 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade numpy

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade numpy

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 1.9.0 (Debian / Ubuntu)

apt-cache madison numpy sudo apt install numpy=<VERSION_BEFORE_1.9.0> sudo apt-mark hold numpy

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list numpy sudo dnf downgrade numpy-<VERSION_BEFORE_1.9.0> sudo dnf versionlock add numpy

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-33430?

numpy: upgrade to newer than 1.9.3. Exact commands for each OS are on this page.

Is CVE-2021-33430 being exploited?

CVE-2021-33430 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-33430 affect?

CVE-2021-33430 affects numpy. Severity is medium (CVSS 5.3). A Buffer Overflow vulnerability exists in NumPy 1.9.x in the PyArray_NewFromDescr_int function of ctors.c when specifying arrays of large dimensions (over 32) from Python code, which could let a malicious user cause a Denial of Service. NOT

How urgent is CVE-2021-33430?

Priority 40/100. Public exploit reference

Software pages

Python vulnerabilities · Pandas and NumPy vulnerabilities

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References

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