CVE-2026-85501

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.

CVSS v3 5.3 MEDIUM

5.3^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 3.9 / Impact : 1.4

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact LOW

Scope UNCHANGED

References

Link	Resource
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-85501.txt	Patch Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*

History

23 Sep 2026, 19:10

Type	Values Removed	Values Added
References	~~() https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-85501.txt -~~	() https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-85501.txt - Patch, Vendor Advisory
First Time		Nlnetlabs Nlnetlabs unbound
CPE		cpe:2.3:a:nlnetlabs:unbound::::::::

Information

Published : 2026-09-16 09:17

Updated : 2026-09-23 19:10

NVD link : CVE-2026-85501

Mitre link : CVE-2026-85501

CVE.ORG link : CVE-2026-85501

JSON object : View

Products Affected

nlnetlabs

unbound

CWE

CWE-770

Allocation of Resources Without Limits or Throttling

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