cryptography: Improper Restriction of Operations within the Bounds of a Memory Buffer
CVE-2026-39892 is a critical-severity improper restriction of operations within the bounds of a memory buffer vulnerability in cryptography from Pyca, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected cryptography versions: >= 45.0.0, < 46.0.7. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.68% chance of exploitation within 30 days, higher than 53% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of cryptography you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Pyca | cryptography | >= 45.0.0, < 46.0.7 | Not stated |
| Red Hat | Red Hat Ansible Automation Platform 2.5 for RHEL 8 | Not specified in the record | Not stated |
| Red Hat | Red Hat Ansible Automation Platform 2.5 for RHEL 9 | Not specified in the record | Not stated |
| Red Hat | Red Hat Ansible Automation Platform 2.6 for RHEL 9 | Not specified in the record | Not stated |
| Red Hat | Red Hat AI Inference Server 3.3 | Not specified in the record | Not stated |
| Red Hat | Red Hat Ansible Automation Platform 2.6 | Not specified in the record | Not stated |
| Red Hat | Red Hat Discovery 2 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux AI 3.3 | Not specified in the record | Not stated |
| Red Hat | Red Hat Hardened Images | Not specified in the record | Not stated |
| Red Hat | Red Hat OpenShift AI 2.25 | Not specified in the record | Not stated |
| Red Hat | Red Hat OpenShift AI 3.3 | Not specified in the record | Not stated |
| Red Hat | Red Hat Quay 3.10 | Not specified in the record | Not stated |
| Red Hat | Red Hat Quay 3.12 | Not specified in the record | Not stated |
| Red Hat | Red Hat Quay 3.14 | Not specified in the record | Not stated |
| Red Hat | Red Hat Quay 3.15 | Not specified in the record | Not stated |
| Red Hat | Red Hat Quay 3.16 | Not specified in the record | Not stated |
| Red Hat | Red Hat Quay 3.17 | Not specified in the record | Not stated |
| Red Hat | Red Hat Quay 3.9 | Not specified in the record | Not stated |
| Red Hat | Red Hat Trusted Artifact Signer 1.4 | Not specified in the record | Not stated |
| Red Hat | Lightspeed Core | Not specified in the record | Not stated |
| Red Hat | Migration Toolkit for Applications 8 | Not specified in the record | Not stated |
| Red Hat | OpenShift Lightspeed | Not specified in the record | Not stated |
| Red Hat | Red Hat AI Inference Server | Not specified in the record | Not stated |
| Red Hat | Red Hat Ansible Automation Platform 2 | Not specified in the record | Not stated |
| Red Hat | Red Hat Ansible Automation Platform Ansible Core 2 | Not specified in the record | Not stated |
Version data comes from the organisation that assigned the CVE; 6 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 6.9 | Medium | CNA (github.com) |
| CVSS 3.1 | 9.8 | Critical | NVD |
| CVSS 3.1 | 7.3 | High | CNA |
Official description
cryptography is a package designed to expose cryptographic primitives and recipes to Python developers. From 45.0.0 to before 46.0.7, if a non-contiguous buffer was passed to APIs which accepted Python buffers (e.g. Hash.update()), this could lead to buffer overflows. This vulnerability is fixed in 46.0.7.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Restriction of Operations within the Bounds of a Memory Buffer
The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary.
How developers prevent this class of flaw
- Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
- Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Other references
- github.com/pypa/advisory-database/tree/main/vulns/cryptography/PYSEC-2026-36.yaml
- 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
Other vulnerabilities in cryptography
- 8.7 High severity
- 8.2 High severity
- 7.5 High severity
- 7.5 High severity
Recent Improper Restriction of Operations within the Bounds of a Memory Buffer vulnerabilities
- 7.5 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.0 High severity
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