CVE-2026-3593
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 · uneditedA use-after-free vulnerability exists within the DNS-over-HTTPS implementation. This issue affects BIND 9 versions 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, and 9.20.9-S1 through 9.20.22-S1. BIND 9 versions 9.18.0 through 9.18.48 and 9.18.11-S1 through 9.18.48-S1 are NOT affected.
In the news
Third-party coverageSurfaced from public web coverage — external links open in a new tab.
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 · moderate confidenceA use-after-free vulnerability exists in BIND 9's DNS-over-HTTPS (DoH) implementation. This memory safety flaw affects versions 9.20.0-9.20.22, 9.21.0-9.21.21, and supported stable releases 9.20.9-S1 through 9.20.22-S1. The 9.18.x stable release line is explicitly NOT affected.
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>= 9.20.0, < 9.20.23>= 9.21.0, < 9.21.22CVSS 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
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 checksWork through these to decide whether this CVE applies to you.
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Identify BIND 9 versionRun 'named -v' or 'named -V' to retrieve the installed BIND version. Alternatively, use package manager commands like 'rpm -q bind' or 'dpkg -l bind9' depending on your system.Affected if The version falls within 9.20.0 through 9.20.22, or 9.21.0 through 9.21.21.
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Confirm DoH is enabledExamine the BIND configuration file (typically named.conf or included configuration files) for DoH-related directives such as 'doh-port', 'dns-over-https', or 'doh' server options. Also check for the 'doh' module being loaded.Affected if DoH is explicitly configured and active in the named.conf files.
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Verify listening DoH portsCheck for open ports associated with DoH (commonly port 443 or custom ports specified in configuration). Use 'netstat -tlnp' or 'ss -tlnp' to list listening ports, and cross-reference with the DoH port numbers defined in your BIND configuration.Affected if A DoH listener is bound to a port and accepting connections.
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Confirm BIND process is runningUse 'ps aux | grep named' or 'systemctl status named' to verify the BIND named process is currently running.Affected if The named process is active and serving DNS queries, which enables the vulnerable DoH code path.
You are affected if BIND 9 version is 9.20.0-9.20.22 or 9.21.0-9.21.21 AND DNS-over-HTTPS is enabled and actively listening.
Generated from the published advisory. Verify against your own configuration.
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 · scoped9.20.239.21.22
Upgrade BIND 9 installations to a version outside the affected range (e.g., 9.18.x stable or a patched 9.20.x/9.21.x release). If DoH cannot be immediately disabled, consider network-level restrictions on DoH endpoints while planning the upgrade.
9.20.23 or later for 9.20.x branches; 9.21.22 or later for 9.21.x branches
- 1. Identify the currently installed BIND 9 version using 'named -v' or 'bind -v'
- 2. For BIND 9.20.x installations: upgrade to version 9.20.23 or later
- 3. For BIND 9.21.x installations: upgrade to version 9.21.22 or later
- 4. Obtain the appropriate package from your distribution's package manager or ISC downloads (https://downloads.isc.org/isc/bind9/)
- 5. Stop the named service: 'systemctl stop named' or 'service named stop'
- 6. Install the new package using your package manager (e.g., 'apt-get install bind9', 'yum update bind', or 'dnf update bind')
- 7. Verify the new version is installed: 'named -v'
- 8. Start the named service: 'systemctl start named' or 'service named start'
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation3.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,040.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-3593 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-3593 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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