CVE-2026-34582: Botan is a C++ cryptography library

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CRITICAL 9.1REMOTEUPGRADE

CVE-2026-34582 is a critical-severity flaw (CVSS 9.1) affecting botan. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 86%)
CISA exploited list	No
Weakness	CWE-841, CWE-166
Published	2026-04-07
Last modified	2026-07-24

Publisher (CNA): GitHub, Inc. · Vendor: botan project

Last updated 2026-07-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-07 22:16 UTCPublished CVE record published
2026-07-24 22:10 UTCUpdated Record last modified

botan project botan UPGRADE

Affected: >= 3.0.0 and <= 3.11.0

Fixed in: newer than 3.11.0

Safe to downgrade to: a release before 3.0.0

1. Check installed version

apt-cache policy botan || rpm -q botan || botan --version

2. UPGRADE to newer than 3.11.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade botan

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade botan

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 3.0.0 (Debian / Ubuntu)

apt-cache madison botan sudo apt install botan=<VERSION_BEFORE_3.0.0> sudo apt-mark hold botan

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list botan sudo dnf downgrade botan-<VERSION_BEFORE_3.0.0> sudo dnf versionlock add botan

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-34582?

botan: upgrade to newer than 3.11.0. Exact commands for each OS are on this page.

Is CVE-2026-34582 being exploited?

CVE-2026-34582 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-34582 affect?

CVE-2026-34582 affects botan. Severity is critical (CVSS 9.1). 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 authentica

How urgent is CVE-2026-34582?

Priority 40/100. Critical severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-44378 HIGH 7.5 UPGRADE Botan is a C++ cryptography library
CVE-2026-34580 HIGH 7.5 DOWNGRADE Botan is a C++ cryptography library
CVE-2026-32884 MEDIUM 5.9 UPGRADE Botan is a C++ cryptography library
CVE-2026-32883 MEDIUM 5.9 UPGRADE Botan is a C++ cryptography library
CVE-2026-32877 HIGH 8.2 UPGRADE Botan is a C++ cryptography library

References

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