8.2

CVE-2026-63576: legion of the bouncy castle inc. bc-csharp Improper Certificate Validation

CVSS: 8.2v4.0HighUndergoing analysis
Published 02-10-2026Last modified 06-10-2026
Open JSON

Vulnerability summary

CVE-2026-63576 is a high (CVSS 8.2) Improper Certificate Validation vulnerability in legion of the bouncy castle inc. bc-csharp. EPSS estimates a 0.22% chance of exploitation in the next 30 days, higher than 11.6% of scored vulnerabilities.

Overall risk
33/100
0100
Medium · default modelHow is this calculated?
CVSS score
8.2/10
010
High · v4.0 (CVE.org)
EPSS score
0.22%
0%100%
Low · Change unavailable
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 02-10-2026
    PublishedVulnerability first disclosed.
  2. 06-10-2026
    Last modifiedVulnerability information updated.

Description

Improper certificate validation in PkixNameConstraintValidator (ExtractHostFromURL) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a name-constrained subordinate CA, or anyone able to obtain certificates with chosen subjectAltName URIs from such a CA, to bypass permitted or excluded uniformResourceIdentifier name constraints during certification path validation via a URI whose path, query, fragment or userinfo contains characters such as '@' or ':', because the host was extracted by string slicing without first isolating the RFC 3986 authority component, so the host compared against the constraints could differ from the URI's actual host.

CVSS metrics

2 scores · 2 sources · 1 version

EPSS trend

Probability

0.22%

Chance of exploitation in the next 30 days

Percentile

12%

Versus all other CVEs

30-day change

Change unavailable

Change unavailable

02-10-202621-10-2026
EPSS score
0.22%

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

Legion of the bouncy castle inc.1 product

1 vendor · 1 product

References

2 links