9.3

CVE-2026-34580: botan_project botan Improper Certificate Validation

CVSS: 9.3v4.0CriticalModified
AliasesALPINE-CVE-2026-34580UBUNTU-CVE-2026-34580
Published 07-04-2026Last modified 15-07-2026
Open JSON

Vulnerability summary

CVE-2026-34580 is a critical (CVSS 9.3) Improper Certificate Validation vulnerability in botan_project botan. EPSS estimates a 0.32% chance of exploitation in the next 30 days, higher than 23.5% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.3/10
010
Critical · v4.0 (CVE.org)
EPSS score
0.32%
0%100%
Low · +0.07 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 07-04-2026
    PublishedVulnerability first disclosed.
  2. 15-07-2026
    Last modifiedVulnerability information updated.

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 metrics

7 scores · 4 sources · 2 versions

EPSS trend

Probability

0.32%

Chance of exploitation in the next 30 days

Percentile

24%

Versus all other CVEs

30-day change

+0.07 pp

From 0.25% on 21-09-2026

21-09-202621-10-2026
EPSS score
0.32%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Ubuntu2 products
  • botanAll versions (No fix recorded)
  • botan3All versions (No fix recorded)
Alpine1 product
  • botan3< 3.11.1-r0
Botan_project1 product
Randombit1 product
  • botan≥ 3.11.0, < 3.11.1

4 vendors · 5 products

References

8 links