Aggregate DNS name chained pointer decompression work leads to degradation of service.

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-96405
StatePUBLISHED
AssignerNLnet Labs
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-21 09:17:08 UTC
Updated2026-10-22 15:22:40 UTC
DescriptionNLnet Labs Unbound up to and including version 1.26.1 limits compression-pointer traversal for each individual domain-name operation but has no aggregate inbound decompression-work budget. Many chained compression pointers in a message results in a lot of CPU usage following them. A malicious actor with recursive-query access and control of an ordinarily delegated authority that serves specially crafted replies can exploit the vulnerability and degrade Unbound's general performance.

Risk And Classification

Primary CVSS: v3.1 5.3 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS: 0.002380000 probability, percentile 0.139580000 (date 2026-10-22)

Problem Types: CWE-770 | CWE-770 CWE-770: Allocation of Resources Without Limits or Throttling

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
3.1CNACVSS5.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

CVSS v3.1 Breakdown

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA NLnet Labs Unbound affected 1.26.2 semver Not specified

References

ReferenceSourceLinkTags
www.nlnetlabs.nl/downloads/unbound/CVE-2026-96405.txt [email protected] www.nlnetlabs.nl
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Yuheng Zhang (Tsinghua University & Jingxian Technology Co., Ltd.) (en)

CNA: Jianjun Chen (Tsinghua University) (en)

CNA: Zihan Wang (Z.AI Co., Ltd.) (en)

CNA: Kaiwen Shen (CloudItera) (en)

Additional Advisory Data

SourceTimeEvent
CNA2026-07-16T00:00:00.000ZIssue reported by Yuheng Zhang
CNA2026-07-17T00:00:00.000ZNLnet Labs shares patch
CNA2026-07-17T00:00:00.000ZYuheng Zhang requests changes
CNA2026-07-21T00:00:00.000ZNLnet Labs shares new patch
CNA2026-09-30T00:00:00.000ZYuheng Zhang verifies patch
CNA2026-09-16T00:00:00.000ZCoordinated fixes released with version 1.26.2

Solutions

CNA: This issue is fixed starting with version 1.26.2

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