Debian LinuxOperating system · Debian
CVE-2021-31866
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 and 4.1.x before 4.1.3 allows an attacker to learn the values of internal authentication keys by observing timing differences in string comparison operations within SysController and MailHandlerController.
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 before 4.0.9 and 4.1.x before 4.1.3 contains a timing attack vulnerability in SysController and MailHandlerController where insecure string comparison (likely using == instead of constant-time comparison) allows attackers to deduce authentication key values by measuring response time differences.
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, < 4.1.3CVSS 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
- Low
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/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 installationLocate the Redmine installation directory and look for a file named VERSION or Gemfile.lock that contains the version number. On Linux systems, common paths include /opt/redmine, /var/www/redmine, or within the application's root directory.Affected if Redmine is installed and the version cannot be determined or is in the vulnerable range
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Determine installed Redmine versionCheck the VERSION file in the Redmine root directory, or run 'bundle exec rake -T' in the Redmine directory to verify the installation, or query the Redmine web interface version if accessible via /admin/infoAffected if Version is less than 4.0.9, or greater than or equal to 4.1.0 but less than 4.1.3
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Verify Debian base system versionIf running a packaged Redmine installation on Debian, check the OS version by running 'cat /etc/debian_version' or 'lsb_release -a'Affected if Running Debian Linux version 9.0 with a Redmine package installed in the vulnerable version range
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Confirm vulnerable controllers are presentIn the Redmine installation, locate the files app/controllers/sys_controller.rb and app/controllers/mail_handler_controller.rb. Examine these files for the presence of string comparison operations using '==' operator for authentication key validation (such as api_key comparison)Affected if The controllers contain insecure string comparison (using == instead of secure_compare or constant-time comparison) and the Redmine version falls within the vulnerable range
The environment is affected if Redmine version is below 4.0.9 or between 4.1.0 and 4.1.3 (inclusive), and the application uses the SysController or MailHandlerController with API key authentication that relies on insecure string comparison.
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 data4.0.94.1.3
Upgrade to Redmine 4.0.9, 4.1.3, or later to obtain the patched version with constant-time string comparison. If immediate upgrade is not feasible, consider network-level restrictions on affected endpoints.
Fix this in Debian Linux
Scoped from the published advisory
- Consultation2.0 h
- Implementation3.0 h
- Testing3.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,512.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-31866 — 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-2021-31866 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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