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BindApplication · Isc

CVE-2023-6516

HIGH · 7.5 CVSS v3.1 Published 2024-02-13
Fix available
A fix is available. Upgrade to after 9.16.45 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
To keep its cache database efficient, `named` running as a recursive resolver occasionally attempts to clean up the database. It uses several methods, including some that are asynchronous: a small chunk of memory pointing to the cache element that can be cleaned up is first allocated and then queued for later processing. It was discovered that if the resolver is continuously processing query patterns triggering this type of cache-database maintenance, `named` may not be able to handle the cleanup events in a timely manner. This in turn enables the list of queued cleanup events to grow infinitely large over time, allowing the configured `max-cache-size` limit to be significantly exceeded. This issue affects BIND 9 versions 9.16.0 through 9.16.45 and 9.16.8-S1 through 9.16.45-S1.

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

In BIND 9 recursive resolvers, cache cleanup operations allocate small memory chunks pointing to cache elements and queue them for asynchronous processing. Under continuous query patterns triggering cleanup, the resolver cannot process cleanup events fast enough, causing the queue to grow unbounded and exceed the configured max-cache-size limit, leading to memory exhaustion and potential denial of service.

MitigationUpgrade BIND 9 to version 9.16.46, 9.16.45-S2, or later; alternatively, upgrade to the stable 9.18 branch or later which is not affected by this issue.

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
BindApplication
Affected:>= 9.16.0, <= 9.16.45= 9.16.8= 9.16.11= 9.16.12= 9.16.13= 9.16.14= 9.16.21= 9.16.32= 9.16.36= 9.16.43= 9.16.45
Active Iq Unified ManagerApplication
Affected:all versions

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. Check installed BIND version
    Run `named -v` or `named -V` to retrieve the BIND version. Compare the version number to the affected range: 9.16.0 through 9.16.45 inclusive.
    Affected if The installed version is 9.16.0 through 9.16.45, or matches any of the specific affected versions listed (9.16.8, 9.16.11, 9.16.12, 9.16.13, 9.16.14, 9.16.21, 9.16.32, 9.16.36, 9.16.43, 9.16.45).
  2. Check for symptom of memory growth
    Monitor the memory usage of the named process over time using tools such as `ps aux | grep named`, `top`, or by querying the BIND statistics channel. Look for continuously increasing RES memory consumption.
    Affected if The named process shows continuously increasing memory usage approaching or exceeding the configured max-cache-size limit under sustained query load.

You are affected if running BIND version 9.16.0 through 9.16.45 as a recursive resolver with cache enabled, and you observe memory growth beyond the configured max-cache-size limit under query load.

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 a release after 9.16.45
Interim mitigation

Upgrade BIND 9 to version 9.16.46, 9.16.45-S2, or later; alternatively, upgrade to the stable 9.18 branch or later which is not affected by this issue.

Recommended fix High confidence

BIND 9.16.46 or later, or migrate to stable release BIND 9.18.x

  1. 1. Identify the current BIND version by running `named -v` or `bind -v`
  2. 2. If running BIND 9.16.0 through 9.16.45, plan an upgrade to version 9.16.46 or later
  3. 3. For production systems, test the upgrade in a staging environment first
  4. 4. Before upgrading, backup the current configuration: `cp -r /etc/bind /etc/bind.backup` (or your equivalent config path)
  5. 5. Stop the named service: `systemctl stop named` or `service named stop`
  6. 6. Install the updated BIND package via your package manager (e.g., `apt-get update && apt-get install bind9` or `yum update bind`)
  7. 7. Verify the new version is installed: `named -v`
  8. 8. Review and validate the configuration file syntax: `named-checkconf /etc/named.conf`
Caveat Ensure configuration compatibility; major version upgrades (e.g., 9.16 to 9.18) may require reviewing configuration syntax changes, particularly in views and ACLs

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

Fix this in Bind Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
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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-2023-6516 in production — separate from our analysis above.

No notes yet

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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