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CRITICAL severity

CVE-2026-82717 — unbound

CRITICAL

CVE-2026-82717 is a critical-severity (CVSS 9.8) CWE-122 vulnerability. A fix is available — see the affected versions and patch details below.

Published
Updated
Affected
1 product
Patched
See advisory
Exploits
None indexed
Exploitation data as of Oct 11, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • A successful exploit gives an attacker total control of the affected component, not partial access.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-82717.

EPSS Exploitation Probability

via FIRST.org ↗
0.8%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs55th percentile — riskier than 55% of all scored CVEsHighest risk
0.28%0.62%0.95%1.28%0.8%0.8%Oct 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-82717 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Description

In NLnet Labs Unbound up to and including 1.26.0, a vulnerability was found in that can progressively corrupt heap memory and under certain systems and compilation options could lead to remote code execution. The vulnerability starts when CNAME synthesis during an upstream response needs to enforce(rewrite) a max TTL value in the packet buffer. Coupled with a compression pointer that points to the overwritten value and invalidates the domain name, it leads to an error path that does not properly move the buffer position and allows for the heap buffer overflow. Since this is heavily reliant on heap memory layout, results are memory corruption that eventually leads to a crash and under specific systems and compilation options remote code execution.

Affected Products

1 product · 1 configurations
Application
unboundnlnetlabs
< 1.26.1
range

Detection & mitigation playbook

Vulnerability

  1. Detect

    Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

  2. Fix

    Upgrade the affected component to the fixed release for CVE-2026-82717, or apply your distribution's backported patch — distro builds are often patched at an older version number, so check your vendor's advisory rather than the upstream version alone.

  3. Workarounds

    Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

This is an Important vulnerability in Unbound that could lead to remote code execution due to heap memory corruption during CNAME synthesis. As Unbound is a critical DNS resolver component in Red Hat environments, successful exploitation could severely impact service availability and integrity. The complexity of…

Workaround published by Red Hat
To mitigate this restrict Unbound to trusted clients and limit which upstream name servers it can query. If Unbound is unused, disable or remove the service. Apply process/cgroup limits to contain crash impact.
Source: Red Hat security advisory for CVE-2026-82717 (CC BY 4.0)
ProductFixed inAdvisory
Red Hat Enterprise Linux 10unbound-0:1.24.2-7.el10_2.6RHSA-2026:71419
Red Hat Enterprise Linux 8unbound-0:1.16.2-5.14.el8_10.4RHSA-2026:70754
Red Hat Enterprise Linux 9unbound-0:1.24.2-3.el9_8.8RHSA-2026:71487
Red Hat OpenShift Container Platform 4.22openshift/ose-rhel-coreos-9:4.22.9.8.202609291947-0RHSA-2026:74428
Red Hat Hardened Imagesunbound-main-1.26.1-1.hum1RHSA-2026:68590

Frequently Asked Questions

In NLnet Labs Unbound up to and including 1.26.0, a vulnerability was found in that can progressively corrupt heap memory and under certain systems and compilation options could lead to remote code execution. The vulnerability starts when CNAME synthesis during an upstream response needs to enforce(rewrite) a max TTL value in the packet buffer. Coupled with a compression pointer that points to the overwritten value and invalidates the domain name, it leads to an error path that does not properly move the buffer position and allows for the heap buffer overflow. Since this is heavily reliant on
O3 Security · Impact-Aware SCA

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CVE-2026-82717: unbound RCE (Critical 9.8)