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Vulnerability record · CVE-2026-34580 · published 7 April 2026

CVE-2026-34580: Botan project botan improper certificate validation vulnerability

Botan Project · Botan

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.

9.3 CVSS 4.0 Critical EPSS 0.32% · top 77.7% CWE-295 · Improper certificate validation
9.3CVSS 4.0 base score
0.32%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References
24 Jul 2026Last modified by NVD

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.

CVSS: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:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/randombit/botan/security/advisories/GHSA-v782-6fq4-q827 Vendor Advisory
https://access.redhat.com/security/cve/CVE-2026-34580
https://bugzilla.redhat.com/show_bug.cgi?id=2456288
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34580.json

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2021-24115Botan project botan vulnerabilityIn Botan before 2.17.3, constant-time computations are not used for certain decoding and encoding operations (base32, base58, base64, and hex).EPSS 2.0%9.8CVE-2018-9127Botan project botan improper certificate validation vulnerabilityBotan 2.2.0 - 2.4.0 (fixed in 2.5.0) improperly handled wildcard certificates and could accept certain certificates as valid for hostnames when, unde…EPSS 0.93%9.8CVE-2017-2801Botan project botan out-of-bounds read vulnerabilityA programming error exists in a way Randombit Botan cryptographic library version 2.0.1 implements x500 string comparisons which could lead to certif…EPSS 1.3%9.8CVE-2015-7826Botan project botan improper certificate validation vulnerabilitybotan 1.11.x before 1.11.22 improperly handles wildcard matching against hostnames, which might allow remote attackers to have unspecified impact via…EPSS 1.1%9.8CVE-2016-6878Botan project botan improper input validation vulnerabilityThe Curve25519 code in botan before 1.11.31, on systems without a native 128-bit integer type, might allow attackers to have unspecified impact via v…EPSS 1.2%9.8CVE-2016-9132Botan project botan integer overflow vulnerabilityIn Botan 1.8.0 through 1.11.33, when decoding BER data an integer overflow could occur, which would cause an incorrect length field to be computed. S…EPSS 2.0%9.8CVE-2016-2196Botan project botan memory buffer overflow vulnerabilityHeap-based buffer overflow in the P-521 reduction function in Botan 1.11.x before 1.11.27 allows remote attackers to cause a denial of service (memor…EPSS 5.3%9.8CVE-2016-2195Botan project botan memory buffer overflow vulnerabilityInteger overflow in the PointGFp constructor in Botan before 1.10.11 and 1.11.x before 1.11.27 allows remote attackers to overwrite memory and possib…EPSS 6.7%

Source: NIST National Vulnerability Database (record CVE-2026-34580), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.