CVE-2026-85501

Public on 2026-09-16
Modified on 2026-09-17
Description
Novel vulnerabilities to launch algorithmic complexity attacks on DNSSEC have been researched under the term 'ReTrap'. These result in degradation of service when malicious zones are used to serve the algorithmic complexity vulnerabilities. NLnet Labs Unbound up to and including 1.26.0 is vulnerable to some of them. TagTrap, where the triple(Zone, Algo, KeyTag) matching mechanism introduces a significant attack vector when resolvers handle malicious responses containing numerous mismatched DNSKEY, RRSIG, and DS record. DelegationTrap, where constructing the chain-of-trust requires iterative validation of DNSKEY and DS records from the root zone downward. For deeply nested domains, this results in significant computational overhead. NsecTrap, where responses with excessive invalid NSEC records compel the resolver to validate each one. AdditionalTrap, where Unbound by default would try to DNSSEC validate the ADDITIONAL section as well. This can be exploited to waste validation resources by malicious users.
Severity
Important severity
Important
See what this means
CVSS v3 Base Score
7.5
See breakdown

Affected Packages

Platform Package Release Date Advisory Status
Amazon Linux 2 - Core unbound 2026-09-28 ALAS2-2026-3941 Fixed
Amazon Linux 2 - Unbound1.17 Extra unbound 2026-09-28 ALAS2UNBOUND-1.17-2026-011 Fixed
Amazon Linux 2023 unbound 2026-09-29 ALAS2023-2026-3127 Fixed
Amazon Linux 2027 Preview unbound 2026-09-28 ALAS2027-2026-106 Fixed

CVSS Scores

Score Type Score Vector
Amazon Linux CVSSv3 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD CVSSv3 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H