CVE-2026-34580: Botan is a C++ cryptography library

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HIGH 7.5REMOTEDOWNGRADE

CVE-2026-34580 is a high-severity flaw (CVSS 7.5) 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. In 3.11.0, the function Certificate_Store::certificate_known had a misleading name; it would return true if any certificate in the store had a DN (and subject key identifier, if set) matching that of the argument. It did not check that the cert it found and the cert it was passed were actually the same certificate. In 3.11.0 an extension of path validation logic was made which assumed that certificate_known on

Why this priority

High severity
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 61%)
CISA exploited list	No
Weakness	CWE-295
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 DOWNGRADE

Affected: 3.11.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.11.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 3.11.0 (Debian / Ubuntu)

apt-cache madison botan sudo apt install botan=<VERSION_BEFORE_3.11.0> sudo apt-mark hold botan

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list botan sudo dnf downgrade botan-<VERSION_BEFORE_3.11.0> 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-2026-34580?

botan: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-34580 being exploited?

CVE-2026-34580 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-2026-34580 affect?

CVE-2026-34580 affects botan. Severity is high (CVSS 7.5). Botan is a C++ cryptography library. In 3.11.0, the function Certificate_Store::certificate_known had a misleading name; it would return true if any certificate in the store had a DN (and subject key identifier, if set) matching that of the

How urgent is CVE-2026-34580?

Priority 41/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-44378 HIGH 7.5 UPGRADE Botan is a C++ cryptography library
CVE-2026-34582 CRITICAL 9.1 UPGRADE 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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