Summary

The DNSSEC validation routines treat entire RRsets of DNSKEY records as trusted once they have established trust in only one of the DNSKEYs. As a result, if a zone includes a DNSKEY with a public key that matches a configured trust anchor, all keys in that zone will be trusted to authenticate other records in the zone. There is a second variant of this vulnerability involving DS records, where an authenticated DS record covering one DNSKEY leads to trust in signatures made by an unrelated DNSKEY in the same zone.

Details

verify_dnskey_rrset() will return Ok(true) if any record's public key matches a trust anchor. This results in verify_rrset() returning a Secure proof. This ultimately results in successfully verifying a response containing DNSKEY records. verify_default_rrset() looks up DNSKEY records by calling handle.lookup(), which takes the above code path. There's a comment following this that says "DNSKEYs were already validated by the inner query in the above lookup", but this is not the case. To fully verify the whole RRset of DNSKEYs, it would be necessary to check self-signatures by the trusted key over the other keys. Later in verify_default_rrset(), verify_rrset_with_dnskey() is called multiple times with different keys and signatures, and if any call succeeds, then its Proof is returned.

Similarly, verify_dnskey_rrset() returns Ok(false) if any DNSKEY record is covered by a DS record. A comment says "If all the keys are valid, then we are secure", but this is only checking that one key is authenticated by a DS in the parent zone's delegation point. This time, after control flow returns to verify_rrset(), it will call verify_default_rrset(). The special handling for DNSKEYs in verify_default_rrset() will then call verify_rrset_with_dnskey() using each KSK DNSKEY record, and if one call succeeds, return its Proof. If there are multiple KSK DNSKEYs in the RRset, then this leads to another authentication break. We need to either pass the authenticated DNSKEYs from the DS covering check to the RRSIG validation, or we need to perform this RRSIG validation of the DNSKEY RRset inside verify_dnskey_rrset() and cut verify_default_rrset() out of DNSKEY RRset validation entirely.

If a certificate had more than one distributionPoint, then only the first distributionPoint would be considered against each CRL's IssuingDistributionPoint distributionPoint, and then the certificate's subsequent distributionPoints would be ignored.

The impact was that correctly provided CRLs would not be consulted to check revocation. With UnknownStatusPolicy::Deny (the default) this would lead to incorrect but safe Error::UnknownRevocationStatus. With UnknownStatusPolicy::Allow this would lead to inappropriate acceptance of revoked certificates.

This vulnerability is thought to be of limited impact. This is because both the certificate and CRL are signed -- an attacker would need to compromise a trusted issuing authority to trigger this bug. An attacker with such capabilities could likely bypass revocation checking through other more impactful means (such as publishing a valid, empty CRL.)

More likely, this bug would be latent in normal use, and an attacker could leverage faulty revocation checking to continue using a revoked credential.

This vulnerability is identified as GHSA-pwjx-qhcg-rvj4. Thank you to @1seal for the report.

Name constraints for URI names were ignored and therefore accepted.

Note this library does not provide an API for asserting URI names, and URI name constraints are otherwise not implemented. URI name constraints are now rejected unconditionally.

Since name constraints are restrictions on otherwise properly-issued certificates, this bug is reachable only after signature verification and requires misissuance to exploit.

This vulnerability is identified as GHSA-965h-392x-2mh5. Thank you to @1seal for the report.

Permitted subtree name constraints for DNS names were accepted for certificates asserting a wildcard name.

This was incorrect because, given a name constraint of accept.example.com, *.example.com could feasibly allow a name of reject.example.com which is outside the constraint. This is very similar to CVE-2025-61727.

Since name constraints are restrictions on otherwise properly-issued certificates, this bug is reachable only after signature verification and requires misissuance to exploit.

This vulnerability is identified as GHSA-xgp8-3hg3-c2mh. Thank you to @1seal for the report.

A panic was reachable when parsing certificate revocation lists via [BorrowedCertRevocationList::from_der] or [OwnedCertRevocationList::from_der]. This was the result of mishandling a syntactically valid empty BIT STRING appearing in the onlySomeReasons element of a IssuingDistributionPoint CRL extension.

This panic is reachable prior to a CRL's signature being verified.

Applications that do not use CRLs are not affected.

Thank you to @tynus3 for the report.

During message encoding, hickory-proto's BinEncoder stores pointers to labels that are candidates for name compression in a Vec<(usize, Vec<u8>)>. The name compression logic then searches for matches with a linear scan.

A malicious message with many records can both introduce many candidate labels, and invoke this linear scan many times. This can amplify CPU exhaustion in DoS attacks.

This is similar to CVE-2024-8508.

We recommend all affected users update to hickory-proto 0.26.1 for the fix.