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CVE-2026-34580

Botan has a certificate authentication bypass due to trust anchor confusion

9.3 CriticalFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

0.46%Up 0.4 points since Apr 8, 2026
90%50%10%1%

What each source reports

CVE List Score used 9.3

Botan has a certificate authentication bypass due to trust anchor confusion

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.

Record
CVE-2026-34580
CVSS 4.0
9.3 CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-295, CWE-295
Updated
2026-11-02
EUVDEUVD-2026-19947 9.3

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.

Record
EUVD-2026-19947
CVSS 4.0
9.3 CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Updated
2026-11-02
NVD 9.3

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.

Record
CVE-2026-34580
CVSS 4.0
9.3 CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-295
Updated
2026-11-02
OSVALPINE-CVE-2026-34580 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 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.

Record
ALPINE-CVE-2026-34580
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Updated
2026-11-02
OSV 9.3

Botan has a certificate authentication bypass due to trust anchor confusion

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.

Record
CVE-2026-34580
CVSS 4.0
9.3 CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Weakness
CWE-295
Updated
2026-11-02
OSVUBUNTU-CVE-2026-34580 9.3

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.

Record
UBUNTU-CVE-2026-34580
CVSS 4.0
9.3 CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
botan3
Alpine:v3.24
before 3.11.1-r0
3.11.1-r0
botan
Ubuntu:18.04:LTS
All versions, plus listed versions
2.4.0-32.4.0-42.4.0-5ubuntu1
None known
botan
Ubuntu:20.04:LTS
All versions, plus listed versions
2.9.0-22.9.0-2build12.12.1-22.12.1-2build1
None known
botan
Ubuntu:Pro:22.04:LTS
All versions, plus listed versions
2.17.3+dfsg-32.19.1+dfsg-2ubuntu12.19.1+dfsg-2ubuntu1+esm1
None known
botan
Ubuntu:Pro:24.04:LTS
All versions, plus listed versions
2.19.3+dfsg-1ubuntu12.19.3+dfsg-1ubuntu22.19.3+dfsg-1ubuntu2+esm1
None known
botan
Ubuntu:25.10
All versions, plus listed versions
2.19.5+dfsg-4
None known
botan3
Ubuntu:25.10
All versions, plus listed versions
3.7.1+dfsg-2
None known
botan3
Ubuntu:26.10
All versions, plus listed versions
3.10.0+dfsg-23.11.1+dfsg-23.12.0+dfsg-2
None known
botan3
Ubuntu:26.04:LTS
All versions, plus listed versions
3.7.1+dfsg-23.10.0+dfsg-2
None known

History

History
RecordedChangedSources
first indexedCVE List, EUVD, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-34580 is a critical vulnerability (CVSS 9.3) in Botan Project Botan, published April 7, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.46%, the 40th percentile. Fixed in botan3 3.11.1-r0.

References

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