CVE-2023-42117
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 · uneditedExim Improper Neutralization of Special Elements Remote Code Execution Vulnerability. This vulnerability allows remote attackers to execute arbitrary code on affected installations of Exim. Authentication is not required to exploit this vulnerability. The specific flaw exists within the smtp service, which listens on TCP port 25 by default. The issue results from the lack of proper validation of user-supplied data, which can result in a memory corruption condition. An attacker can leverage this vulnerability to execute code in the context of the current process. Was ZDI-CAN-17554.
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 confidenceExim contains a memory corruption vulnerability in its SMTP service (port 25) due to improper validation of user-supplied data. Unauthenticated remote attackers can exploit this flaw to execute arbitrary code in the context of the Exim process.
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< 4.96.2CVSS 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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Determine Exim versionRun 'exim --version' or check your package manager (e.g., 'rpm -q exim', 'dpkg -l exim4') to identify the installed Exim version.Affected if The installed version is lower than 4.96.2.
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Confirm Exim is runningCheck if the Exim daemon is active using 'systemctl status exim' or 'ps aux | grep exim'. Also verify it is listening on SMTP port 25 using 'netstat -tlnp | grep :25' or 'ss -tlnp | grep :25'.Affected if Exim is running and listening on port 25.
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Verify network exposureDetermine if port 25 is exposed to untrusted networks by reviewing firewall rules ('iptables -L' or 'ufw status') or network configuration. Check whether the service accepts remote connections.Affected if Port 25 is accessible from untrusted or external network paths.
You are affected if you are running Exim version below 4.96.2, the service is active on port 25, and that port is reachable from network paths where unauthenticated attackers could send malicious SMTP commands.
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 · scoped4.96.2
Update Exim to the latest patched version. If immediate patching is not feasible, restrict or monitor network access to port 25 as a compensating control.
Exim 4.96.2 or later
- Check current Exim version: `exim -version` or `dpkg -l | grep exim`
- Update package lists: `apt update` (Debian/Ubuntu) or equivalent for your distribution
- Upgrade Exim: `apt install exim4` (Debian/Ubuntu) or `yum update exim` (RHEL/CentOS)
- Verify the installed version is 4.96.2 or later: `exim -version`
- Restart Exim service if needed: `systemctl restart exim4` or `systemctl restart exim`
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-42117 — 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-2023-42117 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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- 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
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