CVE-2023-23931

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.

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
python-cryptography	26.04 LTS resolute	Not affected
	25.10 questing	Not affected
	25.04 plucky	Not affected
	24.10 oracular	Not affected
	24.04 LTS noble	Not affected
	23.10 mantic	Not affected
	23.04 lunar	Fixed 38.0.4-2ubuntu0.1
	22.10 kinetic	Ignored end of life, was needed
	22.04 LTS jammy	Fixed 3.4.8-1ubuntu2.1
	20.04 LTS focal	Fixed 2.8-3ubuntu0.2
	18.04 LTS bionic	Fixed 2.1.4-1ubuntu1.4+esm6
	16.04 LTS xenial	Not affected
	14.04 LTS trusty	Not in release

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Notes

mdeslaur

Per the upstream advisory: "This is a soundness bug -- it allows programmers to misuse an API, it cannot be exploited by attacker controlled data alone."

seth-arnold

Debian's update was incomplete, see 2.6.1-3+deb10u4

ccdm94

as per the advisory, this vulnerability was introduced in version 1.8.

charlescochran

The patch uses require_writable=True in from_buffer(), but this wasn't added to python-cffi until 1.12.0 (see commit https://github.com/python-cffi/cffi/commit/4945de3df6a8f3bb2ee903a687f659a92aa8f11e), whereas bionic has 1.11.5-1. As a workaround for the bionic backport, use memoryview to check if the buffer is writable.

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
python-cryptography	Upstream: 9fbf84e

Severity score breakdown

CVSS version: CVSS v3.0

Base score 4.8 · Medium

Base metrics

Parameter	Value
Attack vector	Network
Attack complexity	High
Privileges required	None
User interaction	None
Scope	Unchanged
Confidentiality impact	None
Integrity impact	Low
Availability impact	Low

Scores

Parameter	Value
Base score	4.8 · Medium
Exploitability score	-
Impact score	-

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L

References

Related Ubuntu Security Notices (USN)

USN-6539-1
python-cryptography vulnerabilities
6 December 2023

USN-8776-1
python-cryptography vulnerabilities
16 September 2026