Cipher.update_into can corrupt memory if passed an immutable python object as the outbuf

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.9 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2023-23931: 1.30% estimated exploitation activity in the next 30 days; percentile 70.50 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Previously, Cipher.updateinto 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. This is a soundness bug -- it allows programmers to misuse an API, it cannot be exploited by attacker controlled data alone. This now correctly raises an exception. This issue has been present since updateinto was originally introduced in cryptography 1.8.

Published by the source

7 Feb 2023, 20:54 UTC

Last modified by the source

10 Sep 2026, 03:49 UTC

Source last checked

26 Oct 2026, 13:35 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-w7pp-m8wf-vj6r

2. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-w7pp-m8wf-vj6r

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2023-23931

Advisory: Cipher.update_into can corrupt memory if passed an immutable python object as the outbuf
IDs: CVE-2023-23931, GHSA-w7pp-m8wf-vj6r
Record: https://patchnext.com/advisories/cve-2023-23931 (revision 3, source checked 26 Oct 2026, 13:35 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: cryptography 39.0.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI cryptography: affected >= 1.8, < 39.0.1; fixed in 39.0.1

## Suggested inspection (read-only)
- `python -m pip show cryptography`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on cryptography.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-w7pp-m8wf-vj6r (OSV record GHSA-w7pp-m8wf-vj6r lists affected ranges: PyPI cryptography >=1.8 <39.0.1 (fixed))
- Verified: https://github.com/advisories/GHSA-w7pp-m8wf-vj6r (GitHub-reviewed advisory GHSA-w7pp-m8wf-vj6r lists affected ranges: PyPI cryptography >=1.8 <39.0.1)

Commands are suggestions: review each one before running it.