CVE-2020-28012
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 Exposure of File Descriptor to Unintended Control Sphere because rda_interpret uses a privileged pipe that lacks a close-on-exec flag.
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 version 4.94.2 contains a file descriptor leak in the rda_interpret function. The function creates a privileged pipe without setting the close-on-exec flag, causing the file descriptor to be inherited by child processes spawned by Exim. This exposes the privileged pipe to unintended control spheres, potentially allowing local attackers to access or manipulate the privileged file descriptor.
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 exim -bV to display the version numberAffected if The reported version is 4.00 or higher but lower than 4.94.2
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Identify if rda router is configuredReview Exim configuration files (typically exim.conf) for any router definitions using the rda router or LDA driverAffected if The rda router or any rda-related configuration is present and active in the Exim configuration
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Verify pipe file descriptors in running Exim processesInspect /proc/PID/fd/ for open pipe file descriptors belonging to Exim worker processes, noting any pipes with unusually high descriptor numbersAffected if Exim processes show inherited pipe file descriptors that persist across child process spawning
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Check for child processes with unexpected pipe accessExamine all child processes spawned by Exim (such as filtering utilities or external transports) to determine if they have access to pipe file descriptors beyond what is expected for normal operationAffected if Child processes hold file descriptors to pipes created by the parent Exim process, indicating FD_CLOEXEC is not set
Your environment is affected if you run Exim versions 4.00 through 4.94.1 with the rda router enabled, as the privileged pipe file descriptor will be inherited by child processes.
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 to obtain the patch that adds the close-on-exec flag to the pipe. Alternatively, apply the vendor-supplied patch that modifies rda_interpret to set FD_CLOEXEC on the pipe file descriptor.
- Consultation2.0 h
- Implementation1.0 h
- Testing3.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2020-28012 — 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-2020-28012 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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- Version or environment caveats, and links to real fixes
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