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OpenvpnApplication

CVE-2023-46849

HIGH · 7.5 CVSS v3.1 Published 2023-11-11
Fix available
A fix is available. Upgrade to after 2.11.3 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
Using the --fragment option in certain configuration setups OpenVPN version 2.6.0 to 2.6.6 allows an attacker to trigger a divide by zero behaviour which could cause an application crash, leading to a denial of service.

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

OpenVPN versions 2.6.0 through 2.6.6 contain a divide-by-zero vulnerability in the handling of the --fragment configuration option. When this option is used in certain setups, the application will crash due to the divide-by-zero condition, resulting in a denial of service.

MitigationUpgrade OpenVPN to version 2.6.7 or later, or avoid using the --fragment option in vulnerable versions until patching can be performed.

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
OpenvpnApplication
Affected:>= 2.6.0, <= 2.6.6
Openvpn Access ServerApplication
Affected:>= 2.11.0, <= 2.11.3= 2.12.0= 2.12.1
Debian LinuxOperating system
Affected:= 12.0
FedoraOperating system
Affected:= 39

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 OpenVPN version
    Run 'openvpn --version' or 'openvpn --help' to display the version number
    Affected if Version is between 2.6.0 and 2.6.6 inclusive, or is 2.11.0-2.11.3, 2.12.0, or 2.12.1 (Access Server)
  2. Verify --fragment option is configured
    Inspect OpenVPN configuration files (typically in /etc/openvpn/) for the 'fragment' directive, or check running config with 'openvpn --show-config' if the service can be queried
    Affected if The 'fragment' directive is present in any active OpenVPN configuration
  3. Confirm the OpenVPN process is running
    Check for running OpenVPN processes using 'ps aux | grep openvpn' or 'systemctl status openvpn'
    Affected if OpenVPN is actively running with a vulnerable version and fragment option enabled
  4. Check OS distribution version
    If running Debian 12.0 or Fedora 39, check with 'cat /etc/os-release' or 'hostnamectl'
    Affected if OS is Debian 12.0 or Fedora 39 with bundled OpenVPN matching affected versions

You are affected if OpenVPN version is 2.6.0-2.6.6 (or Access Server 2.11.0-2.11.3/2.12.0-2.12.1) AND the --fragment option is configured and active.

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 2.11.3
Interim mitigation

Upgrade OpenVPN to version 2.6.7 or later, or avoid using the --fragment option in vulnerable versions until patching can be performed.

Recommended fix High confidence

OpenVPN 2.6.7+ or OpenVPN Access Server 2.12.2+ (and corresponding patched packages from Debian/Fedora)

  1. 1. Identify all OpenVPN installations in your environment that use version 2.6.0 through 2.6.6, including both server and client configurations
  2. 2. Identify OpenVPN Access Server installations using versions 2.11.0-2.11.3, 2.12.0, or 2.12.1
  3. 3. For OpenVPN 2.6.x: Upgrade to version 2.6.7 or later from the official OpenVPN download page or your distribution's package repository
  4. 4. For OpenVPN Access Server: Upgrade to version 2.12.2 or later from the official OpenVPN Access Server downloads
  5. 5. After upgrading, verify that the --fragment option (if used) functions correctly in your configuration
  6. 6. Test VPN connectivity to ensure the upgrade did not introduce configuration incompatibilities
  7. 7. Apply OS-level updates for Debian 12.0 and Fedora 39 systems to receive the vendor-packaged fixes
Caveat Minor: Review any custom --fragment configuration after upgrade to ensure proper functionality; the upgrade is low-risk as it addresses a denial-of-service vulnerability

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

Fix this in Openvpn Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
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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-2023-46849 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