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RatpackApplication · Ratpack Project

CVE-2021-29485

HIGH · 8.8 CVSS v3.1 Published 2021-06-29
Fix available
A fix is available. Upgrade to 1.9.0 or later.
See remediation →
94/100
Remediation priority · Urgent
Remotely reachable Zero-click

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 · unedited
Ratpack is a toolkit for creating web applications. In versions prior to 1.9.0, a malicious attacker can achieve Remote Code Execution (RCE) via a maliciously crafted Java deserialization gadget chain leveraged against the Ratpack session store. If one's application does not use Ratpack's session mechanism, it is not vulnerable. Ratpack 1.9.0 introduces a strict allow-list mechanism that mitigates this vulnerability when used. Two possible workarounds exist. The simplest mitigation for users of earlier versions is to reduce the likelihood of attackers being able to write to the session data store. Alternatively or additionally, the allow-list mechanism could be manually back ported by providing an alternative implementation of `SessionSerializer` that uses an allow-list.

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 confidence

Ratpack versions prior to 1.9.0 are vulnerable to Java deserialization attacks via the session store, allowing remote code execution through maliciously crafted gadget chains. The vulnerability is exploitable only when the application's session mechanism is in use. Version 1.9.0 introduces a strict allow-list for serialized classes, effectively blocking the attack vector.

MitigationUpgrade to Ratpack 1.9.0 or later to receive the built-in allow-list protection. If upgrading is not feasible, manually implement an allow-listed SessionSerializer or ensure the session data store is inaccessible to attackers.

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
RatpackApplication
Affected:< 1.9.0

CVSS 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
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed Ratpack version
    Check your project's dependency management file (such as build.gradle, pom.xml, or a similar dependency declaration) for the Ratpack library version, or run a dependency resolution command to list the loaded Ratpack version.
    Affected if The reported version is earlier than 1.9.0 (for example, 1.8.0, 1.7.0, etc.)
  2. Confirm session mechanism is active
    Inspect your application configuration and code to determine whether session handling is enabled. Look for session store configuration, session persistence setup, or usage of Ratpack's Session API in the application code.
    Affected if The application's session mechanism is in use and the Ratpack version is below 1.9.0
  3. Check for custom SessionSerializer
    Review your codebase for any custom implementation of SessionSerializer or similar session serialization configuration that may be in use.
    Affected if A custom SessionSerializer is implemented without an allow-list and the Ratpack version is vulnerable
  4. Examine session data store exposure
    Evaluate whether the session data store (such as Redis, JDBC, or another session backend) is exposed to untrusted inputs or accessible to external attackers.
    Affected if The session store accepts untrusted serialized data from potentially malicious sources and the Ratpack version is below 1.9.0

You are affected if your Ratpack version is below 1.9.0 AND your application uses the session mechanism with a session store accessible to potentially malicious serialized data.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Upgrade available Upgrade to 1.9.0 or later
Fixed in 1.9.0
Interim mitigation

Upgrade to Ratpack 1.9.0 or later to receive the built-in allow-list protection. If upgrading is not feasible, manually implement an allow-listed SessionSerializer or ensure the session data store is inaccessible to attackers.

Recommended fix High confidence

Ratpack 1.9.0

  1. Locate your project's build configuration file (pom.xml for Maven or build.gradle for Gradle)
  2. Update the Ratpack dependency version from your current version to 1.9.0
  3. For Maven, change the version in the <version> tag to 1.9.0; for Gradle, update the version string to '1.9.0'
  4. Run your build tool to resolve the new dependency (e.g., mvn clean install or ./gradlew build)
  5. Verify your application still functions correctly, particularly any session-related functionality
  6. Test that session serialization/deserialization works as expected with the new allow-list mechanism
Caveat Review release notes for 1.9.0 to check for any API changes that may affect your application

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Ratpack Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-29485 in production — separate from our analysis above.

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What this is

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.

What belongs here
  • 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
  • No spam, self-promotion, credentials, or personal data