CVE-2026-39892

Critical

Published: 08 April 2026

Published

08 April 2026

Modified

15 April 2026

KEV Added

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Patch

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CVSS Score 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Score 0.0002 6.7th percentile

Risk Priority 20 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-39892 is a critical-severity Improper Restriction of Operations within the Bounds of a Memory Buffer (CWE-119) vulnerability in Cryptography.Io Cryptography. Its CVSS base score is 9.8 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 6.7th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 RA-5 (Vulnerability Monitoring and Scanning) and SI-2 (Flaw Remediation).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190). What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-2 Flaw Remediation good match

preventrecover

Directly mandates timely flaw remediation by patching the buffer overflow vulnerability in cryptography versions 45.0.0 to before 46.0.7.

SI-16 Memory Protection partial match

prevent

Provides defense-in-depth against buffer overflow exploitation through memory protections like ASLR, DEP, and stack canaries.

RA-5 Vulnerability Monitoring and Scanning good match

detect

Enables identification of vulnerable cryptography library installations via vulnerability scanning and monitoring.

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

Why these techniques?

Remote unauthenticated buffer overflow in cryptography Python library enables arbitrary code execution, directly facilitating exploitation of public-facing applications using the vulnerable buffer-accepting APIs like Hash.update().

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

NVD 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.

Deeper analysisAI

CVE-2026-39892 is a buffer overflow vulnerability (CWE-119) in the cryptography Python package, which exposes cryptographic primitives and recipes to Python developers. The flaw affects versions from 45.0.0 up to but not including 46.0.7, where passing a non-contiguous buffer to APIs accepting Python buffers, such as Hash.update(), can trigger buffer overflows.

The vulnerability carries a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), indicating it is exploitable remotely over the network by any unauthenticated attacker with low attack complexity and no user interaction. Exploitation could lead to high impacts on confidentiality, integrity, and availability, such as arbitrary code execution or system crashes via the buffer overflow.

The issue is addressed in cryptography version 46.0.7. Additional mitigation details are available in the GitHub security advisory at https://github.com/pyca/cryptography/security/advisories/GHSA-p423-j2cm-9vmq and the oss-security mailing list post at http://www.openwall.com/lists/oss-security/2026/04/08/12.