Vulnerability in Botan Project

CVE-2026-34582

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.

Published · last modified .

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.004 (30.3th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 30th percentile — 30.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-34582: held from 0.002 to 0.004.

EPSS over last 30 days · oldest: 0.002 · newest: 0.004 · change: +0.001

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-34582?
CVE-2026-34582 is a critical-severity vulnerability in Botan Project, classified under Improper Enforcement of Behavioral Workflow. CVSS score: 9.1/10. Published 2026-04-07.
How severe is CVE-2026-34582?
Critical severity. CVSS v3 base score is 9.1 out of 10.