CVE-2026-34582

Modified Modified - Updated After Analysis

TLS 1.3 Authentication Bypass in Botan Cryptography Library

Publication date: 2026-04-07

Last updated on: 2026-06-30

Assigner: GitHub, Inc.

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.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-04-07

Last Modified

2026-06-30

Generated

2026-07-06

AI Q&A

2026-04-08

EPSS Evaluated

2026-07-05

NVD

CVE-2026-34582

Affected Vendors & Products

Vendor	Product	Version / Range
botan_project	botan	From 3.0.0 (inc) to 3.11.0 (inc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-166	The product receives input from an upstream component, but it does not handle or incorrectly handles when an expected special element is missing.
CWE-841	The product supports a session in which more than one behavior must be performed by an actor, but it does not properly ensure that the actor performs the behaviors in the required sequence.

Attack-Flow Graph

Mitigation Strategies

The vulnerability is fixed in Botan version 3.11.1. Immediate mitigation involves upgrading the Botan cryptography library to version 3.11.1 or later.

Executive Summary

This vulnerability exists in the Botan C++ cryptography library's TLS 1.3 implementation prior to version 3.11.1. It allows ApplicationData records to be processed before the Finished message is received during a TLS handshake.

Specifically, a server that enforces client authentication via certificates can be bypassed by a client that omits sending the Certificate, CertificateVerify, and Finished messages, and instead sends application data records directly.

This means the client can skip the authentication steps and still have its application data processed, which is a security flaw.

Impact Analysis

This vulnerability can allow an attacker to bypass client authentication on a server using Botan's TLS 1.3 implementation prior to version 3.11.1.

As a result, unauthorized clients could send application data without proving their identity, potentially leading to unauthorized access or data exposure.

This undermines the security guarantees of TLS client authentication and could compromise the confidentiality and integrity of communications.

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