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Vulnerability · Published Apr 7, 2026 · Assigned by GitHub_M

CVE-2026-34582Botan has a TLS 1.3 certificate authentication bypass

Critical 9.1

In plain English

A critical-severity security flaw in botan from randombit. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 15% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)9.1Critical
Exploit odds (30 days)0.2%top 84.5% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Alpine:v3.24botan33.11.1-r0ALPINE-CVE-2026-34582
Debian:13botan33.11.0+dfsg-2DEBIAN-CVE-2026-34582
Debian:14botan33.11.0+dfsg-2DEBIAN-CVE-2026-34582
Ubuntu:25.10botanno fix listedUBUNTU-CVE-2026-34582
Ubuntu:25.10botan3no fix listedUBUNTU-CVE-2026-34582
Ubuntu:26.04:LTSbotan3no fix listedUBUNTU-CVE-2026-34582
Ubuntu:26.10botan3no fix listedUBUNTU-CVE-2026-34582

Affected products (as reported)

VendorProductVersions
randombit botan < 3.11.1

Weakness: CWE-841, CWE-166 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

References