CVE-2023-23931
MEDIUMCVE-2023-23931 is a medium-severity (CVSS 4.8) CWE-754 vulnerability in cryptography. 1 public exploit reference exists, so weaponization risk is real. O3 Security confirms whether CVE-2023-23931 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Cipher.update_into can corrupt memory in pyca cryptography
Blast Radius
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 | 39.0.1 |
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. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
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 pinpoints whether CVE-2023-23931 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
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.
Frequently Asked Questions
Is CVE-2023-23931 in your dependencies?
O3 detects CVE-2023-23931 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.