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CVE-2026-39892: Cryptography vulnerable to buffer overflow if non-contiguous buffers were passed to APIs

April 8, 2026 (updated November 4, 2026)

If a non-contiguous buffer was passed to APIs which accepted Python buffers (e.g. Hash.update()), this could lead to buffer overflows. For example:

h = Hash(SHA256())
b.update(buf[::-1])

would read past the end of the buffer on Python >3.11

References

  • access.redhat.com/errata/RHSA-2026:19375
  • access.redhat.com/errata/RHSA-2026:20338
  • access.redhat.com/errata/RHSA-2026:21017
  • access.redhat.com/errata/RHSA-2026:22465
  • access.redhat.com/errata/RHSA-2026:22629
  • access.redhat.com/errata/RHSA-2026:22840
  • access.redhat.com/errata/RHSA-2026:23361
  • access.redhat.com/errata/RHSA-2026:24483
  • access.redhat.com/errata/RHSA-2026:24761
  • access.redhat.com/errata/RHSA-2026:24762
  • access.redhat.com/errata/RHSA-2026:24853
  • access.redhat.com/errata/RHSA-2026:24866
  • access.redhat.com/errata/RHSA-2026:24977
  • access.redhat.com/errata/RHSA-2026:30088
  • access.redhat.com/errata/RHSA-2026:30089
  • access.redhat.com/errata/RHSA-2026:37275
  • access.redhat.com/errata/RHSA-2026:42644
  • access.redhat.com/errata/RHSA-2026:43651
  • access.redhat.com/errata/RHSA-2026:43670
  • access.redhat.com/errata/RHSA-2026:43851
  • access.redhat.com/errata/RHSA-2026:43853
  • access.redhat.com/errata/RHSA-2026:43854
  • access.redhat.com/errata/RHSA-2026:43855
  • access.redhat.com/errata/RHSA-2026:46956
  • access.redhat.com/errata/RHSA-2026:7295
  • access.redhat.com/security/cve/CVE-2026-39892
  • bugzilla.redhat.com/show_bug.cgi?id=2456735
  • github.com/advisories/GHSA-p423-j2cm-9vmq
  • github.com/pyca/cryptography/commit/622d672e429a7cff836a23c5903683dbec1901f5
  • github.com/pyca/cryptography/commit/c09d38ae52de7d95fe683b7a7c496f5751616f27
  • github.com/pyca/cryptography/security/advisories/GHSA-p423-j2cm-9vmq
  • github.com/pypa/advisory-database/tree/main/vulns/cryptography/PYSEC-2026-36.yaml
  • nvd.nist.gov/vuln/detail/CVE-2026-39892
  • security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-39892.json

Code Behaviors & Features

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Affected versions

All versions starting from 45.0.0 before 46.0.7

Fixed versions

  • 46.0.7

Solution

Upgrade to version 46.0.7 or above.

Impact 9.8 CRITICAL

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

Learn more about CVSS

Weakness

  • CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer
  • CWE-131: Incorrect Calculation of Buffer Size

Source file

pypi/cryptography/CVE-2026-39892.yml

Spotted a mistake? Edit the file on GitLab.

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