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CVE-2026-85501: CWE-770: Allocation of Resources Without Limits or Throttling in NLnet Labs Unbound

0
Medium
VulnerabilityCVE-2026-85501cvecve-2026-85501cwe-770
Published: 09/16/2026 (09/16/2026, 08:32:25 UTC)
Source: CVE Database V5
Vendor/Project: NLnet Labs
Product: Unbound

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.

CVSS v3.1

Score 5.3medium

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected software

NLnet Labs

Unbound

Affected versions
>=0 <1.26.1

Technical Details

Data Version
5.2
Assigner Short Name
NLnet Labs
Date Reserved
2026-09-07T14:06:21.977Z
Cvss Version
3.1
State
PUBLISHED

Threat ID: 6aaa578955bf5e2cf540b1fe

Added to database: 09/16/2026, 08:47:05 UTC

Last updated: 09/16/2026, 08:47:05 UTC

Views: 1

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