CVE-2026-63577 (GCVE-0-2026-63577)

Vulnerability from cvelistv5 – Published: 2026-10-02 07:07 – Updated: 2026-10-02 07:07
VLAI
Title
Name Constraints bypass: directoryName constraint matched at any position in the DN instead of as a prefix
Summary
Improper certificate validation in the directoryName name-constraint check (PkixNameConstraintValidator.WithinDNSubtree) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an attacker who controls, or can have certificates issued by, a name-constrained intermediate CA to get certificates accepted by PKIX path validation whose subject distinguished name, or a directoryName subjectAltName, lies outside the CA's permitted subtrees, via a name that places other RDNs ahead of a copy of the permitted RDN sequence, because the check looks for the constraint's first RDN anywhere in the name and compares the remaining RDNs from that position, instead of requiring the constraint to be an initial prefix of the name as RFC 5280 sections 4.2.1.10 and 7.1 require.
Severity
8.2 (High)
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
CWE
  • CWE-295 - Improper Certificate Validation
Assigner
References
Impacted products
Vendor Product Version CPE status
Legion of the Bouncy Castle Inc. bc-csharp Affected: 0 , < 2.7.0 (semver)
guessed Create a notification for this product.
Credits
Discovered by Claude, Anthropic's AI assistant, and triaged by the Anthropic security team in collaboration with Anthropic Research.
Show details on NVD website
To clipboard 

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          "vendor": "Legion of the Bouncy Castle Inc.",
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}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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