dbcve.org
EximApplication

CVE-2020-28016

HIGH · 7.8 CVSS v3.1 Published 2021-05-06
Fix available
A fix is available. Upgrade to 4.94.2 or later.
See remediation →
80/100
Remediation priority · High
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
Exim 4 before 4.94.2 allows an off-by-two Out-of-bounds Write because "-F ''" is mishandled by parse_fix_phrase.

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

Exim 4 before 4.94.2 contains an off-by-two out-of-bounds write vulnerability in the parse_fix_phrase function when handling the -F '' command-line argument. This memory corruption issue allows local or remote attackers to potentially execute arbitrary code or cause a denial of service via specially crafted input.

MitigationUpgrade Exim to version 4.94.2 or later. If immediate patching is not possible, restrict access to the Exim service and ensure proper input validation is in place.

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
EximApplication
Affected:>= 4.00, < 4.94.2

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
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/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 --version' or check the exim binary version to determine the installed release
    Affected if The installed version is 4.00 or higher but below 4.94.2
  2. Check for Exim daemon running
    Identify if the Exim MTA daemon is actively running on the system
    Affected if Exim is running as a daemon and the version is within the affected range
  3. Examine -F argument usage
    Review Exim configuration and startup scripts to determine if the -F command-line argument is used when invoking Exim
    Affected if Exim is invoked with the -F argument and the version is vulnerable
  4. Verify parse_fix_phrase function exposure
    The vulnerability exists in the parse_fix_phrase function when processing the -F argument; confirm Exim handles this argument type
    Affected if Exim processes -F arguments and the version is before 4.94.2

A system is affected if Exim version 4.00 through 4.94.1 is installed and the -F command-line argument is used or can be passed to the Exim binary.

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.

From vendor data
Upgrade available Upgrade to 4.94.2 or later
Fixed in 4.94.2
Interim mitigation

Upgrade Exim to version 4.94.2 or later. If immediate patching is not possible, restrict access to the Exim service and ensure proper input validation is in place.

Fix this in Exim Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing4.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,720
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,752.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2020-28016 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2020-28016 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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