CVE-2023-23931 is a medium-severity (CVSS 4.8) CWE-754 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.
Cipher.update_into can corrupt memory in pyca cryptography
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-23931.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2023-23931 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,238 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
cryptographyReal-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. In affected versions Cipher.update_into would accept Python objects which implement the buffer protocol, but provide only immutable buffers. This would allow immutable objects (such as bytes) to be mutated, thus violating fundamental rules of Python and resulting in corrupted output. This now correctly raises an exception. This issue has been present since update_into was originally introduced in cryptography 1.8.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | cryptography | ≥ 1.8&&< 39.0.1 | 39.0.1pip install --upgrade 'cryptography==39.0.1' |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
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.
Fix
Update cryptography to 39.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-23931 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.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2023-23931 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2023-23931. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
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.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Ansible Automation Platform 2.4 for RHEL 8 | python3x-cryptography-0:38.0.4-2.el8ap | RHSA-2023:4693 |
| Red Hat Ansible Automation Platform 2.4 for RHEL 8 | automation-controller-0:4.4.3-1.el8ap | RHSA-2023:4971 |
| Red Hat Enterprise Linux 8 | python39:3.9-8100020240214182535.7044f6c1 | RHSA-2024:2985 |
| Red Hat Enterprise Linux 8 | python-cryptography-0:3.2.1-6.el8 | RHSA-2023:7096 |
| Red Hat Enterprise Linux 9 | python-cryptography-0:36.0.1-4.el9 | RHSA-2023:6615 |
| Red Hat Quay 3 | quay/quay-rhel8:v3.10.0-150 | RHSA-2023:7341 |
| Red Hat Software Collections for Red Hat Enterprise Linux 7 | rh-python38-python-cryptography-0:2.8-6.el7 | RHSA-2023:6793 |
Frequently Asked Questions
Is CVE-2023-23931 in your dependencies?
O3 Security finds CVE-2023-23931 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.