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CRITICAL severity

PyCA Cryptography symmetrically encrypting large values can lead to integer overflowGHSA-rhm9-p9w5-fwm7

CRITICALFix: pyca/cryptography@82b6ce2

GHSA-rhm9-p9w5-fwm7 is a critical-severity (CVSS 9.1) CWE-190 vulnerability in cryptography. 1 public exploit reference exists, so weaponization risk is real. A fix is available for cryptography — see the affected versions and patch details below.

Also known asCVE-2020-36242PYSEC-2021-63
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Oct 12, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
6.7%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs94th percentile — riskier than 94% of all scored CVEsHighest risk
0.00%2.78%5.57%8.35%1.3%6.7%Apr 26Aug 26Oct 26

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

How urgent is this, really

GHSA-rhm9-p9w5-fwm7 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 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
🐍cryptography

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

cryptography is a package designed to expose cryptographic primitives and recipes to Python developers. When certain sequences of update() calls with large values (multiple GBs) for symetric encryption or decryption occur, it's possible for an integer overflow to happen, leading to mishandling of buffers. This is patched in version 3.3.2 and newer.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPIcryptography≥ 3.1&&< 3.3.23.3.2pip install --upgrade 'cryptography==3.3.2'

Affected Products

3 products · 3 configurations
Application
cryptographycryptography.io
< 3.3.2
range
OS
fedorafedoraproject
1 version
33
Application
communications cloud native core network function cloud native environmentoracle
1 version
1.10.0
Exploits & PoCs
1

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

In the cryptography package before 3.3.2 for Python, certain sequences o…

github.comNVDJul 2021

Detection & mitigation playbook

Open-source dependency

  1. Detect

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

  2. Fix

    Update cryptography to 3.3.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-rhm9-p9w5-fwm7 is resolved across your whole dependency graph.

  3. Workarounds

    Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

Triggering this flaw on in versions of python-cryptography as shipped with Red Hat Enterprise Linux 8 BaseOS, Appstream, as well as Red Hat Software Collections, can result in denial of service due to memory consumption or MemoryError exception. In Red Hat OpenStack Platform, because the flaw has a lower impact and…

Workaround published by Red Hat
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Source: Red Hat security advisory for GHSA-rhm9-p9w5-fwm7 (CC BY 4.0)
ProductFixed inAdvisory
Red Hat Enterprise Linux 8python-cryptography-0:3.2.1-4.el8RHSA-2021:1608
Red Hat Software Collections for Red Hat Enterprise Linux 7rh-python38-babel-0:2.7.0-12.el7RHSA-2021:3254
Red Hat Virtualization 4 for Red Hat Enterprise Linux 8redhat-virtualization-host-0:4.4.6-20210527.3.el8_4RHSA-2021:2239

Frequently Asked Questions

cryptography is a package designed to expose cryptographic primitives and recipes to Python developers. When certain sequences of `update()` calls with large values (multiple GBs) for symetric encryption or decryption occur, it's possible for an integer overflow to happen, leading to mishandling of buffers. This is patched in version 3.3.2 and newer.
O3 Security · Impact-Aware SCA

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