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Critical · 9.3 CVE-2026-34580 EUVD-2026-19947

Botan has a certificate authentication bypass due to trust anchor confusion

Published Apr 7, 2026 · Updated Jul 15, 2026 · Assigned by GitHub_M

Description

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 only returned true if the certificates were in fact identical. The impact is that if an end entity certificate is presented, and its DN (and subject key identifier, if set) match that of any trusted root, the end entity certificate is accepted immediately as if it itself were a trusted root. , This vulnerability is fixed in 3.11.1.

Affected products

VendorProductAffectedFixed
randombit botan >= 3.11.0, < 3.11.1 —

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

ReleasePackageFixed inAdvisory
Ubuntu 26.10 botan3 No fix yet —
Ubuntu 26.04 LTS botan3 No fix yet —
Ubuntu 25.10 botan +1 No fix yet —
Ubuntu 20.04 LTS botan No fix yet —
Ubuntu 18.04 LTS botan No fix yet —
Show 2 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
Ubuntu Pro 24.04 LTS botan No fix yet —
Ubuntu Pro 22.04 LTS botan No fix yet —
ReleasePackageFixed inAdvisory
Alpine v3.24 botan3 3.11.1-r0 —

References