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

Advisory record · `GHSA-w7pp-m8wf-vj6r`

- **Identifiers:** `GHSA-w7pp-m8wf-vj6r` · `CVE-2023-23931` · `PYSEC-2023-11`
- **State:** Confirmed
- **Severity:** CVSS 4.8 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-754](https://cwe.mitre.org/data/definitions/754.html)
- **Tags:** [CWE-754](https://agentprime.io/advisories/tag/cwe-754.md)
- **Published:** 7 Feb 2023
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 7 Feb 2023, 20:54 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `cryptography` (PyPI): affected `>=1.8, <39.0.1`; fixed in `39.0.1`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> Cryptography versions from 1.8 up to but not including 39.0.1 are affected: Cipher.update_into would accept immutable buffer objects such as bytes as its output buffer, allowing them to be mutated. An attacker cannot exploit this with attacker-controlled data alone; it requires a programmer to misuse the API. Upgrade to cryptography 39.0.1 or later, which raises an exception in this case.

Written 5 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 4.8 Medium, CVSS 3.1: `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.013, the 70th percentile, on 9 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 7 Feb 2023, 19:48 UTC: [Published by the maintainers as a GitHub repository advisory](https://github.com/pyca/cryptography/security/advisories/GHSA-w7pp-m8wf-vj6r)
- 31 Oct 2026, 14:37 UTC: First seen by agentprime
- 31 Oct 2026, 14:37 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-w7pp-m8wf-vj6r)

## Sources

- [GitHub Advisory Database: GHSA-w7pp-m8wf-vj6r](https://github.com/advisories/GHSA-w7pp-m8wf-vj6r)
- [OSV: GHSA-w7pp-m8wf-vj6r](https://osv.dev/vulnerability/GHSA-w7pp-m8wf-vj6r)
- <https://github.com/pyca/cryptography/security/advisories/GHSA-w7pp-m8wf-vj6r>
- <https://nvd.nist.gov/vuln/detail/CVE-2023-23931>
- <https://github.com/pyca/cryptography/pull/8230>
- <https://github.com/pyca/cryptography/commit/d6951dca25de45abd52da51b608055371fbcde4e>
- <https://github.com/pyca/cryptography>
- <https://github.com/pypa/advisory-database/tree/main/vulns/cryptography/PYSEC-2023-11.yaml>
- <https://lists.debian.org/debian-lts-announce/2024/10/msg00012.html>
- <https://security.netapp.com/advisory/ntap-20230324-0007>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-w7pp-m8wf-vj6r>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-w7pp-m8wf-vj6r/>. Everything for agents: <https://agentprime.io/llms.txt>.