CVE-2020-28007
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 4 before 4.94.2 allows Execution with Unnecessary Privileges. Because Exim operates as root in the log directory (owned by a non-root user), a symlink or hard link attack allows overwriting critical root-owned files anywhere on the filesystem.
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 4 before 4.94.2 runs as root in a log directory owned by a non-root user, enabling symlink or hard link attacks that can overwrite arbitrary root-owned files anywhere on the filesystem, achieving privilege escalation.
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>= 4.00, < 4.94.2CVSS 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
- 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 checksWork through these to decide whether this CVE applies to you.
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Check installed Exim versionRun 'exim --version' or check your package manager (dpkg -l exim, rpm -q exim) to find the exact version numberAffected if Version is 4.00 or higher but lower than 4.94.2
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Identify Exim log directory locationCheck Exim configuration file (typically /etc/exim/exim.conf or /etc/exim4/exim4.conf) for 'log_file_path' or 'log_directory' directive, or inspect the system's syslog configurationAffected if Log directory path is configurable and may be owned by a non-root user
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Verify log directory ownershipRun 'ls -ld' on the Exim log directory path found in the configuration, or check /var/log/exim if using default pathsAffected if The log directory is owned by a non-root user rather than root or the exim user
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Confirm Exim runs as rootCheck the Exim daemon process: run 'ps aux | grep exim' or 'ps -U exim' to see the user the exim daemon runs underAffected if Exim daemon runs as root (typical default behavior in vulnerable versions)
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Check for symlink/hardlink protectionReview Exim configuration for 'verify = strict' or check if system-wide symlink protection (fs.symlink=0) is disabled in /proc/sys/fsAffected if Exim writes logs to a directory owned by a non-root user AND runs as root AND no strict file verification is configured
You are affected if Exim version is below 4.94.2 AND the log directory is owned by a non-root user while Exim runs as root, allowing potential privilege escalation via symlink or hard link attacks.
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.
From vendor data4.94.2
Upgrade Exim to version 4.94.2 or later, and ensure log directories are owned by root or the exim user rather than untrusted non-root users to prevent symlink/hardlink attacks.
- Consultation2.0 h
- Implementation3.0 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-2020-28007 — 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-2020-28007 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
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