dbcve.org
UnboundApplication · Nlnetlabs

CVE-2026-41292

HIGH · 7.5 CVSS v3.1 Published 2026-05-20
Fix available
A fix is available. Upgrade to 1.25.1 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
NLnet 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).

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Unbound up to version 1.25.0 lacks limits on incoming EDNS options in DNS queries. An attacker sending queries with excessively long lists of EDNS options causes threads to become blocked while parsing and creating internal data structures, leading to resource exhaustion and denial of service.

MitigationUpgrade to Unbound 1.25.1 or later, which enforces a limit of 100 incoming EDNS options per query.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
UnboundApplication
Affected:< 1.25.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Verify Unbound is installed
    Run 'unbound -V' or 'unbound-control status' to confirm Unbound DNS resolver is present on the system
    Affected if Unbound is not installed then this CVE does not apply to the environment
  2. Determine installed Unbound version
    Execute 'unbound -V 2>&1 | grep version' or 'unbound-control status' to retrieve the exact version number of the installed Unbound instance
    Affected if The installed version is 1.25.0 or lower (any version less than 1.25.1)
  3. Confirm EDNS support is enabled
    Check the Unbound configuration file (commonly /etc/unbound/unbound.conf) for 'edns-size' or 'do-edns' settings, or run 'unbound-control get_option edns-size' to verify EDNS is not disabled
    Affected if EDNS support is enabled (the default setting) - the vulnerability only affects queries processed with EDNS parsing enabled
  4. Check for signs of resource exhaustion
    Review Unbound logs (typically /var/log/unbound/unbound.log or syslog) for error messages such as 'out of memory', 'thread stalled', or excessive resource usage related to query handling
    Affected if Logs show repeated thread starvation, memory allocation failures, or unusual query processing delays coinciding with incoming DNS traffic

The environment is affected if Unbound is installed with a version lower than 1.25.1 and EDNS support is enabled, as this allows the vulnerability to be exploited through specially crafted DNS queries with excessive EDNS options.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 1.25.1 or later
Fixed in 1.25.1
Interim mitigation

Upgrade to Unbound 1.25.1 or later, which enforces a limit of 100 incoming EDNS options per query.

Recommended fix High confidence

Unbound 1.25.1

  1. Check current Unbound version using: unbound -V or unbound-control status
  2. Upgrade Unbound to version 1.25.1 or later. For source builds, download from nlnetlabs.nl or use your distribution's package manager
  3. If using a package manager (e.g., yum, apt, brew), run: yum update unbound or apt-get install unbound=1.25.1 (or latest available)
  4. Restart the Unbound service: systemctl restart unbound or service unbound restart
  5. Verify the new version is installed: unbound -V
  6. Confirm the EDNS option limit is enforced (default limit is 100 options)
Caveat The upgrade introduces a limit of 100 incoming EDNS options per query. Legitimate configurations relying on more than 100 EDNS options may need adjustment, though this is unlikely in normal deployments.

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Unbound Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,390
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-41292 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data