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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 17 Mar 2022.
Ubuntu LinuxOperating system · Canonical

CVE-2019-16928

CRITICAL · 9.8 CVSS v3.1 Published 2019-09-27
Fix available
A fix is available. Upgrade to after 4.92.2 or later.
See remediation →
100/100
Remediation priority · Urgent
In the wild Public exploit Remotely reachable No privileges Zero-click Patch available

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
Exim 4.92 through 4.92.2 allows remote code execution, a different vulnerability than CVE-2019-15846. There is a heap-based buffer overflow in string_vformat in string.c involving a long EHLO command.

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

Heap-based buffer overflow in Exim's string_vformat function in string.c, triggered by sending a specially crafted long EHLO command, allowing remote code execution. This affects Exim versions 4.92 through 4.92.2 and is distinct from CVE-2019-15846.

MitigationUpgrade Exim to a version newer than 4.92.2 or apply the vendor patch to address the heap-based buffer overflow in the string_vformat function.

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
Ubuntu LinuxOperating system
Affected:= 19.04
Debian LinuxOperating system
Affected:= 10.0
FedoraOperating system
Affected:= 29= 30= 31
EximApplication
Affected:>= 4.92, <= 4.92.2

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
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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify Exim version
    Run 'exim -v' or 'exim --version' to obtain the installed Exim version number
    Affected if Version is 4.92, 4.92.1, or 4.92.2
  2. Verify Exim service is running
    Run 'systemctl status exim' or 'ps aux | grep exim' to confirm the Exim daemon is actively running
    Affected if Exim process is running as an SMTP daemon
  3. Confirm SMTP exposure
    Check if port 25 (or configured SMTP port) is listening externally using 'netstat -tlnp | grep :25' or 'ss -tlnp | grep :25'
    Affected if SMTP port is accessible from network (not bound to localhost only)
  4. Validate version range
    Compare installed version against affected range: version >= 4.92 AND version <= 4.92.2
    Affected if Installed version falls within the vulnerable range 4.92 to 4.92.2 inclusive

Your environment is affected if Exim version 4.92 through 4.92.2 is running and exposed as an accessible SMTP server.

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 4.92.2
Vendor patch bugs.exim.org →
Interim mitigation

Upgrade Exim to a version newer than 4.92.2 or apply the vendor patch to address the heap-based buffer overflow in the string_vformat function.

Recommended fix High confidence

Exim 4.92.3 or later

  1. Check the current Exim version using: exim -v -r 2>&1 | head -1
  2. Upgrade Exim to version 4.92.3 or later using the system's package manager (apt-get update && apt-get install exim4 for Debian/Ubuntu, or dnf update exim for Fedora)
  3. After upgrading, restart the Exim service: systemctl restart exim (or systemctl restart exim4 depending on the package)
  4. Verify the new version is installed: exim -v -r 2>&1 | head -1
  5. Ensure Exim is running properly: systemctl status exim
Caveat Minor risk: review Exim configuration files for compatibility; standard configuration files typically remain compatible across patch versions

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

Fix this in Ubuntu Linux Exploited in the wild — priority engagement
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing8.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,800
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Scan for this in your stack

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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-2019-16928 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