CVE-2023-23931Public exploit

Output corruption via unchecked immutable output buffer

Published Feb 7, 2023 · Updated Nov 3, 2025

Memory corruption in Cipher.update_into in cryptography 1.8 through 39.0.0 allows callers to mutate immutable output buffers. The OpenSSL cipher backend passed outbuf to CFFI without requiring a writable buffer, allowing encryption output to overwrite a bytes object. Reachability requires application code to pass an immutable buffer as outbuf; attacker-controlled data alone cannot trigger the condition.

CVSS severity6.5
Medium
EPSS probability1.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Memory corruption in Cipher.update_into in cryptography 1.8 through 39.0.0 allows callers to mutate immutable output buffers. The OpenSSL cipher backend passed outbuf to CFFI without requiring a writable buffer, allowing encryption output to overwrite a bytes object. Reachability requires application code to pass an immutable buffer as outbuf; attacker-controlled data alone cannot trigger the condition.

The record

CVE
CVE-2023-23931
Published
Feb 7, 2023
Updated
Nov 3, 2025
Vendor
Python Cryptographic Authority
Product
cryptography
Classifications
CWE-754
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Feb 7, 2023CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>=1.8, < 39.0.1

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

Python Cryptographic Authority · cryptographyversion=>=1.8, < 39.0.1

Published CVSS scores

6.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
4.8GitHub Security AdvisoryCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-754Improper Check for Unusual or Exceptional Conditions

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo