dbcve.org
UnboundApplication · Nlnetlabs

CVE-2026-32792

MEDIUM · 5.3 CVSS v3.1 Published 2026-05-20
Fix available
A fix is available. Upgrade to 1.25.1 or later.
See remediation →
62/100
Remediation priority · Elevated
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 1.6.2 up to and including version 1.25.0 has a denial of service vulnerability when compiled with DNSCrypt support ('--enable-dnscrypt'). A bad DNSCrypt query could underflow Unbound's DNSCrypt packet reading procedure that may lead to heap overflow. A malicious actor can exploit the vulnerability with a single bad DNSCrypt query that its decrypted plaintext consists entirely of '0x00' bytes and does not contain the expected '0x80' marker. Unbound would then start reading more bytes than necessary until it finds a non-'0x00' byte. Based on the underlying memory allocator and the memory layout, it could lead to heap overflow while reading followed by a crash. Likelihood of a crash is low, since it relies heavily on the underlying memory allocator and the memory layout. If the heap overflow does not happen, Unbound's later packet checks will deny the packet. Unbound 1.25.1 contains a patch with a fix to bound reading in the given buffer space.

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 DNS resolver versions 1.6.2 through 1.25.0 contain a heap overflow vulnerability in the DNSCrypt packet reading procedure when compiled with DNSCrypt support. A malformed DNSCrypt query with plaintext consisting entirely of 0x00 bytes and missing the expected 0x80 marker triggers an integer underflow, causing Unbound to read beyond buffer bounds into heap memory.

MitigationUpgrade Unbound to version 1.25.1 or later, or if DNSCrypt is not required, recompile Unbound without '--enable-dnscrypt' to eliminate the attack surface.

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:>= 1.6.2, < 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
Low

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

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. Identify installed Unbound version
    Run 'unbound -V' or 'unbound-control version' to retrieve the exact version number
    Affected if The version is >= 1.6.2 and < 1.25.1
  2. Locate Unbound configuration file
    Check common configuration paths such as /etc/unbound/unbound.conf or /etc/unbound/conf.d/ for DNSCrypt-related settings
    Affected if DNSCrypt is explicitly enabled in the configuration file
  3. Verify DNSCrypt provider configuration
    Search the configuration for 'dnscrypt' or 'provider' directives to confirm a DNSCrypt provider is configured
    Affected if A DNSCrypt provider is configured and active, meaning Unbound will process DNSCrypt queries
  4. Confirm Unbound service is running
    Check process list (ps aux) or service status (systemctl/status) to verify the Unbound service is actively running
    Affected if Unbound is running and would be processing incoming DNSCrypt packets

You are affected if Unbound version is between 1.6.2 and 1.25.0 inclusive, DNSCrypt is enabled in configuration, and the service is running to process DNSCrypt queries.

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 Unbound to version 1.25.1 or later, or if DNSCrypt is not required, recompile Unbound without '--enable-dnscrypt' to eliminate the attack surface.

Recommended fix High confidence

Unbound 1.25.1

  1. 1. Identify the current installed version of Unbound using 'unbound -V' or your system's package manager
  2. 2. If Unbound is compiled with DNSCrypt support ('--enable-dnscrypt'), it is vulnerable
  3. 3. Obtain Unbound version 1.25.1 or later from your distribution's package repository or from www.nlnetlabs.nl/downloads/unbound/
  4. 4. Upgrade Unbound to version 1.25.1 using your system's package manager (e.g., 'apt-get update && apt-get install unbound' for Debian/Ubuntu, 'yum update unbound' for RHEL/CentOS)
  5. 5. If building from source, download the 1.25.1 source tarball and compile with your existing configuration options
  6. 6. Restart the Unbound service to load the updated version
  7. 7. Verify the new version is running using 'unbound -V'
Caveat No breaking changes expected; this is a patch release within the 1.x branch

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
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
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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-2026-32792 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