Debian LinuxOperating system · Debian
CVE-2021-31865
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 · uneditedRedmine before 4.0.9, 4.1.x before 4.1.3, and 4.2.x before 4.2.1 allows users to circumvent the allowed filename extensions of uploaded attachments.
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 confidenceRedmine contains a file upload validation bypass where the allowlist of permitted filename extensions for attachments can be circumvented, potentially allowing users to upload files with dangerous extensions that should be blocked.
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
Debian LinuxOperating system
= 9.0< 4.0.9>= 4.1.0, < 4.1.3>= 4.2.0, < 4.2.1CVSS 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
- None
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
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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Identify Redmine installation versionCheck the Redmine version by viewing the VERSION file in the Redmine root directory, or by running 'bundle exec rake redmine:version' from the Redmine directory, or checking the Gemfile.lock for the redmine gem version.Affected if The installed version is less than 4.0.9, or between 4.1.0 and 4.1.3 exclusive, or between 4.2.0 and 4.2.1 exclusive.
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Confirm attachment uploads are enabledCheck the Redmine configuration file config/configuration.yml or config/settings.yml for the attachments settings. Look for 'attachments' section and verify that upload functionality is not explicitly disabled.Affected if Attachment uploads are enabled and the version is in the vulnerable range.
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Review allowed filename extensions for attachmentsAccess Redmine administration settings through the web interface at Administration > Settings > Attachments, or inspect the Redmine database settings table for the 'attachments_allowed_extensions' setting.Affected if The allowed extensions list exists and includes extensions that should be blocked (the vulnerability allows bypassing the allowlist).
You are affected if your Redmine version is below 4.0.9, between 4.1.0-4.1.3, or between 4.2.0-4.2.1, and you have attachment uploads enabled.
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 data4.0.94.1.34.2.1
Upgrade Redmine to version 4.0.9, 4.1.3, or 4.2.1 or later to patch the filename extension validation bypass.
Fix this in Debian Linux
Scoped from the published advisory
- Consultation2.0 h
- Implementation3.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-31865 — 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-2021-31865 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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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.
- 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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