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