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Wildcard DNS Certificates Not Verified Correctly with Excluded DNS Constraints
DEBIAN-CVE-2026-33810
Summary
A security issue affects how certain certificate chains are verified. Specifically, it overlooks wildcard DNS certificates if their domain name doesn't match the case of the excluded DNS constraint. This only impacts trusted certificates issued by certain root CAs. To mitigate, update your certificate verification process to handle this edge case.
What to do
No fix is available yet. Check with your software vendor for updates.
Affected software
| Vendor | Product | Affected versions | Fix available |
|---|---|---|---|
| debian | golang-1.26 | All versions | – |
Original title
When verifying a certificate chain containing excluded DNS constraints, these constraints are not correctly applied to wildcard DNS SANs which use a different case than the constraint. This only af...
Original description
When verifying a certificate chain containing excluded DNS constraints, these constraints are not correctly applied to wildcard DNS SANs which use a different case than the constraint. This only affects validation of otherwise trusted certificate chains, issued by a root CA in the VerifyOptions.Roots CertPool, or in the system certificate pool.
- https://security-tracker.debian.org/tracker/CVE-2026-33810 Vendor Advisory
Published: 8 Apr 2026 · Updated: 8 Apr 2026 · First seen: 8 Apr 2026