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TI-2026-58665 Aliases CVE-2026-85501GHSA-qwgf-hj58-8c2w

Retrap: Novel Vulnerabilities to launch Algorithmic Complexity Attacks on DNSSEC

Priority LOW 39CWE-770Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Partial Red Hat: 1 fixed, 7 without a fix

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-770.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00482 41st percentileScored 2026-11-07
Fix Partial Unbound (NLnet Labs): 1.26.1Red Hat: 1 advisoryRed Hat: 1 fixed, 7 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
NLnet LabsUnboundbefore 1.26.11.26.1Patch availableCNA
  • Unbound VendorNLnet Labs Affected before 1.26.1 Fixed in 1.26.1 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*before 1.26.1VulnerableNLNETLABS
  • cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:* Versions before 1.26.1 Vulnerable ·NLNETLABS

Remediation

  • Fix · CNA Unbound (NLnet Labs) Fixed in 1.26.1

Red Hat 1 advisory

  • RHSA-2026:68590 Released 2026-09-17 · Red Hat rating Critical
    Red Hat Hardened Images RPMs bug fix and enhancement update
    • Red Hat Hardened Images python3-unbound-1.26.1-1.hum1@aarch64, python3-unbound-1.26.1-1.hum1@x86_64, unbound-1.26.1-1.hum1@aarch64 +14

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    NLnet Labs Unbound 1.26.1

    9 records Highest priority Priority MEDIUM 2 MEDIUM, 7 LOW

    Other records, highest priority first

    • TI-2026-56302 Heap buffer overflow and possible Remote Code Execution when digesting DNSKEYPriority MEDIUM 49
    • TI-2026-57038 CNAME synthesis could lead to heap corruptionPriority MEDIUM 40
    • TI-2026-56296 Possible heap buffer overflow during DNSSEC canonicalizationPriority LOW 39
    Show all 9 records →

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 10AffectedNo fix yet: Fix deferred
Red Hat Enterprise Linux 6AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux 7AffectedNo fix yet: Fix deferred
Red Hat Enterprise Linux 8AffectedNo fix yet: Fix deferred
Red Hat Enterprise Linux 9AffectedNo fix yet: Fix deferred
Red Hat OpenShift Container Platform 4AffectedNo fix yet: Fix deferred
Red Hat OpenShift Container Platform 5AffectedNo fix yet: Fix deferred
Red Hat Hardened ImagesFixed RHSA-2026:68590

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-85501
  2. 2026-10-03 Alias added: GHSA-qwgf-hj58-8c2w
  3. 2026-11-06 Affected versions changed · Red Hat

References

Patch 1

  • TI-2026-25690 Possible arbitrary code execution during DNSSEC validation CVSS 4.0CRITICAL 9.1
  • TI-2026-56302 Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY CVSS 4.0CRITICAL 9.1
  • TI-2026-31146 Crash during DNSSEC validation of malicious content CVSS 4.0HIGH 8.7
  • TI-2026-31135 Heap overflow with multiple NSID, COOKIE, PADDING EDNS options CVSS 4.0HIGH 8.7
  • TI-2026-36436 Routinator crashes on specifically crafted RRDP XML files CVSS 4.0HIGH 8.7
  • TI-2026-36433 Routinator exits when accepting an incoming HTTP or RTR connection fails CVSS 4.0HIGH 8.7
See all 96 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences