Actionpack Page CachingApplication · Rubyonrails
CVE-2020-8159
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 · uneditedThere is a vulnerability in actionpack_page-caching gem < v1.2.1 that allows an attacker to write arbitrary files to a web server, potentially resulting in remote code execution if the attacker can write unescaped ERB to a view.
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 confidenceThe actionpack_page-caching gem versions before 1.2.1 contain a file write vulnerability that allows an attacker to write arbitrary files to the web server filesystem. If the attacker can write unescaped ERB templates, this can lead to remote code execution.
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
Actionpack Page CachingApplication
< 1.2.1
Debian LinuxOperating system
= 9.0CVSS 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
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/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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Identify if actionpack_page-caching gem is installedRun 'gem list actionpack_page-caching' or check the Gemfile.lock for the actionpack_page-caching entryAffected if The gem is present in the application dependencies
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Determine the installed gem versionRun 'gem list actionpack_page-caching' to see the installed version number, or inspect the version in Gemfile.lockAffected if The version is lower than 1.2.1 (e.g., 1.2.0, 1.1.0, etc.)
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Verify page caching is enabled in the applicationCheck for 'caches_page' directives in the application's controllers, or look for page caching configuration in config/environments/*.rb filesAffected if Page caching is actively enabled and used in the Rails application
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Check if user-supplied content can influence cached file pathsInspect the controller actions using 'caches_page' to see if request parameters (params) or user input are used in the cached page pathsAffected if User input or dynamic parameters are used to construct cached page paths without proper sanitization
A user is affected if they have actionpack_page-caching gem version below 1.2.1 installed AND page caching is enabled with user input potentially influencing cached file paths.
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.
dbcve · scoped1.2.1
Upgrade the actionpack_page-caching gem to version 1.2.1 or later to remediate this vulnerability.
actionpack_page-caching gem version >= 1.2.1
- Check the current version of actionpack_page-caching gem in your project (examine Gemfile.lock)
- Update the actionpack_page-caching gem to version 1.2.1 or later in your Gemfile
- Run `bundle update actionpack_page-caching` to apply the upgrade
- Verify the updated version is correctly installed by checking Gemfile.lock
- Test the application thoroughly, especially any page caching functionality
- Deploy the updated application
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Actionpack Page Caching
Scoped from the published advisory
- Consultation1.0 h
- Implementation1.0 h
- Testing2.0 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 $1,376.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-8159 — 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-2020-8159 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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