Improper Certificate Validation Affecting bouncycastle.cryptography package, versions [,2.7.0)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-DOTNET-BOUNCYCASTLECRYPTOGRAPHY-20537029
- published6 Oct 2026
- disclosed2 Oct 2026
Introduced: 2 Oct 2026
NewCVE-2026-63577 (opens in a new tab)How to fix?
Upgrade BouncyCastle.Cryptography to version 2.7.0 or higher.
Overview
Affected versions of this package are vulnerable to Improper Certificate Validation via the WithinDNSubtree method in PkixNameConstraintValidator.cs. An attacker who controls, or can obtain certificates from, a name-constrained intermediate CA can have a certificate accepted by PKIX path validation by placing unrelated RDNs before a copy of the permitted distinguished-name sequence, causing a subject DN or directoryName subjectAltName outside the allowed subtree to pass the name-constraints check.
Workarounds
- Ensure
X509Sgp22NameConstraintsis not enabled unless you explicitly need the relaxed GSMA SGP.22 matching behavior; leaving it disabled keepsdirectoryNamename-constraint checks on the strict RFC 5280 prefix-matching path and blocks certificates that try to satisfy a constraint by prepending unrelated RDNs.