External risk intelligence

Python cryptography Buffer Overflow Vulnerability

CVE advisorySeverity: MEDIUM (CVSS 6.9)

CVE-2026-39892

The `cryptography` package is affected by a buffer overflow vulnerability when non-contiguous buffers are passed to specific APIs. If this is reachable, it could potentially lead to memory corruption. Developers should be aware of this issue when using the package.

Memory Corruption

Cryptography Io Cryptography

45.0.0 to before 46.0.7

Halo Surface Signal

Very unlikely · external exposure

1Halo Surface Signal

This vulnerability exists in a software library used by developers to build applications. It is not a standalone service, gateway, or internet-facing appliance. Exposure depends entirely on how a developer integrates the library into their specific application code, making it an internal/developer-centric component rather than a directly exposed network surface.

Horizon Alert

Summary of the vulnerability and why it matters

A potential issue has been identified in the cryptography package, which is used by developers for cryptographic functions. If specific types of data buffers are handled in a certain way, it could lead to memory overflow. The primary concern is to determine if this library is in use within our organization and, if so, to understand the potential exposure.

A code flaw could allow unexpected memory access.
Leadership should be aware of potential software library risks.
Confirm relevance and assess any potential exposure.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by sending specially crafted data to applications that use a vulnerable version of the cryptography library. This could lead to buffer overflows, potentially allowing for code execution or denial of service, depending on how the vulnerable API is used within the application.

No authentication or special access needed.
Non-contiguous buffer passed to APIs.
Possible code execution or denial of service.

Live Threat

Current exploitation, exposure, and threat context

When supported by the advisory, passing a non-contiguous buffer to specific Python buffer APIs within the `cryptography` library could lead to buffer overflows. This affects applications that utilize these APIs for operations like hashing.

Affected: Python buffer APIs in cryptography.
How: Passing non-contiguous buffers to APIs.
Consequence: Potential for buffer overflows.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability resides within the `cryptography` Python package, impacting applications that utilize non-contiguous buffers with specific API calls. Responsibility for addressing this issue likely falls to application development teams and potentially platform or infrastructure teams responsible for managing Python environments and dependencies. The initial step should be to identify all applications and services leveraging the affected `cryptography` package, confirm their exposure and business criticality, and then plan remediation by coordinating with development and vendor management as necessary.

Application and platform teams should own.
Verify `cryptography` package usage and scope.
Plan coordinated dependency updates.

Supplementary metadata

PCI scan relevance

Yes

CVE-2026-39892 — Halo PCI Relevance: Yes. Under typical PCI ASV external scan criteria, this issue may be flagged for scan prioritization.

This buffer overflow vulnerability in the cryptography package could allow an attacker to cause a buffer overflow, potentially leading to remote code execution, which would cause a PCI ASV scan to fail.

Scan-prioritization guidance only—not a PCI DSS certification or ASV attestation.

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is the cryptography package in Python?

The cryptography package is a foundational library that provides Python developers with ready-to-use cryptographic primitives and secure recipes. It is widely used to handle encryption, decryption, and hashing tasks within applications. Because it is a library rather than a standalone program, it functions as a building block integrated directly into other software projects to manage sensitive data operations.

What does CWE-119 mean for CVE-2026-39892?

CWE-119 refers to Improper Restriction of Operations within the Bounds of a Memory Buffer. In the context of CVE-2026-39892, this means the software does not correctly verify the size or structure of data it processes. When the library receives specific types of memory buffers that are not stored in a continuous block, it can write data outside of its assigned memory space, leading to a buffer overflow.

How is this buffer overflow triggered?

The vulnerability is triggered when an application passes a non-contiguous buffer—data stored in scattered memory locations—to specific affected APIs, such as Hash.update(). If you only use standard, contiguous memory buffers or do not process data through these specific cryptographic functions in a way that creates non-contiguous input, this bug is not triggered.

Do I need to worry about this vulnerability?

Relevance depends on your specific application design. According to Halo Surface Signal, this is a developer-centric library rather than an internet-facing appliance. Because it is embedded in code, exposure is not automatic; it relies entirely on how your application handles data input. You should evaluate if your custom applications pass non-contiguous buffers to the library's cryptographic functions.

When should I update my cryptography package?

You should plan to update if your environment uses any version from 45.0.0 up to, but not including, 46.0.7. The first step is to perform a dependency audit across your software portfolio to identify where this library is included. Once identified, coordinate with your development teams to test and apply the version 46.0.7 update, which includes the necessary fix for these memory handling issues.

References

Written by Nicholas Merritt

External-surface CVE analysis and Halo Surface Signal prioritization for Halo Threat Intelligence.