CVE-2026-34582

Critical

Published: 07 April 2026

Published

07 April 2026

Modified

17 April 2026

KEV Added

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Patch

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CVSS Score 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS Score 0.0003 9.7th percentile

Risk Priority 18 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-34582 is a critical-severity Improper Enforcement of Behavioral Workflow (CWE-841) vulnerability in Botan Project Botan. Its CVSS base score is 9.1 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 9.7th 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 SI-2 (Flaw Remediation) and RA-5 (Vulnerability Monitoring and Scanning).

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

prevent

Directly requires identification, reporting, and timely remediation of known flaws like CVE-2026-34582 by patching Botan to version 3.11.1.

SC-23 Session Authenticity partial match

prevent

Protects communications session authenticity by ensuring TLS handshakes complete properly before processing application data, mitigating bypass of client certificate authentication.

RA-5 Vulnerability Monitoring and Scanning partial match

detect

Enables regular vulnerability scanning to identify TLS 1.3 implementation flaws such as premature ApplicationData processing in vulnerable Botan versions.

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?

The vulnerability directly enables remote exploitation of a TLS server (public-facing application) by bypassing mandatory client certificate authentication during the TLS 1.3 handshake, allowing unauthorized access without credentials or interaction.

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

NVD Description

Botan is a C++ cryptography library. Prior to version 3.11.1, the TLS 1.3 implementation allowed ApplicationData records to be processed prior to the Finished message being received. A server which is attempting to enforce client authentication via certificates can by…

bypassed by a client which entirely omits Certificate, CertificateVerify, and the Finished message and instead sends application data records. This vulnerability is fixed in 3.11.1.

Deeper analysisAI

CVE-2026-34582 affects Botan, a C++ cryptography library, specifically its TLS 1.3 implementation in versions prior to 3.11.1. The vulnerability (CWE-841) enables the processing of ApplicationData records before the Finished message is received during the TLS handshake. This flaw allows a server enforcing client authentication via certificates to be bypassed, as rated with a CVSS v3.1 base score of 9.1 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N).

A remote attacker acting as a TLS client can exploit this by omitting the Certificate, CertificateVerify, and Finished messages entirely, instead sending ApplicationData records directly. No privileges or user interaction are required, enabling low-complexity network-based attacks against vulnerable Botan-based servers. Successful exploitation bypasses mandatory client certificate authentication, potentially granting unauthorized access to protected resources and compromising confidentiality and integrity.

The Botan security advisory at https://github.com/randombit/botan/security/advisories/GHSA-pxcj-9ppx-g86g details the issue and confirms the fix in version 3.11.1, recommending immediate upgrades for all users of affected versions implementing TLS 1.3 servers with client certificate requirements.