Long list of incoming EDNS options degrades performance

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Summary

CVECVE-2026-41292
StatePUBLISHED
AssignerNLnet Labs
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-20 10:16:27 UTC
Updated2026-06-30 03:19:25 UTC
DescriptionNLnet Labs Unbound up to and including version 1.25.0 is vulnerable to a degradation of service attack related to parsing long lists of incoming EDNS options. An adversary sending queries with too many EDNS options can hold Unbound threads hostage while they are parsing and creating internal data structures for the options. Coordinated attacks can result in degradation and/or denial of service. Unbound 1.25.1 contains a patch with a fix to limit acceptable incoming EDNS options (100).

Risk And Classification

Primary CVSS: v4.0 6.6 MEDIUM from [email protected]

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Red

EPSS: 0.005560000 probability, percentile 0.423280000 (date 2026-07-04)

Problem Types: CWE-407 | CWE-770 | CWE-1050 | CWE-407 CWE-407: Inefficient Algorithmic Complexity | CWE-770 CWE-770: Allocation of Resources Without Limits or Throttling | CWE-1050 Excessive Platform Resource Consumption within a Loop

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary6.6MEDIUMCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/C...
4.0CNACVSS6.6MEDIUMCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U...
3.1[email protected]Primary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1ADPCVSS7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.10b0ca135-0b70-47e7-9f44-1890c2a1c46cSecondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
None
Confidentiality
None
Integrity
None
Availability
High
Sub Conf.
None
Sub Integrity
None
Sub Availability
None

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Red

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Nlnetlabs Unbound All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA NLnet Labs Unbound affected 1.25.1 semver Not specified
ADP Red Hat Red Hat Enterprise Linux 10 Not specified Not specified
ADP Red Hat Red Hat Enterprise Linux 6 Not specified Not specified
ADP Red Hat Red Hat Enterprise Linux 7 Not specified Not specified
ADP Red Hat Red Hat Enterprise Linux 8 Not specified Not specified
ADP Red Hat Red Hat Enterprise Linux 9 Not specified Not specified
ADP Red Hat Red Hat Hardened Images Not specified Not specified
ADP Red Hat Red Hat OpenShift Container Platform 4 Not specified Not specified
ADP Red Hat Red Hat OpenStack Platform 16.2 Not specified Not specified
ADP Red Hat Red Hat OpenStack Platform 17.1 Not specified Not specified
ADP Red Hat Red Hat OpenStack Platform 18.0 Not specified Not specified
ADP Red Hat Red Hat Data Grid 8 Not specified Not specified
ADP Red Hat Red Hat JBoss Enterprise Application Platform Expansion Pack Not specified Not specified

References

ReferenceSourceLinkTags
bugzilla.redhat.com/show_bug.cgi 0b0ca135-0b70-47e7-9f44-1890c2a1c46c bugzilla.redhat.com
www.nlnetlabs.nl/downloads/unbound/CVE-2026-41292.txt [email protected] www.nlnetlabs.nl Mitigation, Vendor Advisory
security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-41292.json 0b0ca135-0b70-47e7-9f44-1890c2a1c46c security.access.redhat.com
access.redhat.com/security/cve/CVE-2026-41292 0b0ca135-0b70-47e7-9f44-1890c2a1c46c access.redhat.com
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: GitHub user N0zoM1z0 (en)

CNA: Qifan Zhang (Palo Alto Networks) (en)

Additional Advisory Data

SourceTimeEvent
CNA2026-01-11T00:00:00.000ZIssue reported by N0zoM1z0
CNA2026-01-12T00:00:00.000ZNLnet Labs shares patch
CNA2026-01-13T00:00:00.000ZN0zoM1z0 verifies patch
CNA2026-04-26T00:00:00.000ZIssue also reported by Qifan Zhang
CNA2026-04-28T00:00:00.000ZNLnet Labs shares same patch
CNA2026-04-29T00:00:00.000ZQifan Zhang verifies patch
CNA2026-05-20T00:00:00.000ZFixes released with version 1.25.1
ADP2026-05-20T10:00:54.433ZReported to Red Hat.
ADP2026-05-20T09:19:13.022ZMade public.

Solutions

CNA: This issue is fixed starting with version 1.25.1

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