Security readout for executives and security teams
Plain-English summary
Ratpack apps using client-side sessions before 1.9.0 may have used a predictable default cookie signing key based on application startup time. If an attacker can write cookies and infer that time, session data could be modified when encryption is not enabled. The supplied sources do not report active exploitation.
Executive priority
Treat this as a targeted remediation item, not an emergency. The impact is session integrity risk in specific Ratpack configurations, with no supplied evidence of active exploitation. Prioritize upgrading or replacing default keys for affected production applications.
Technical view
The client-side session config defaulted the signing key to application startup time. In Ratpack <1.9.0, this weak default could permit cookie/session tampering when client-side session encryption is absent. Ratpack 1.9.0 changed the default to a securely random startup-generated value; the vendor workaround is to supply an alternative signing key.
Likely exposure
Exposure is limited to applications using ratpack/ratpack <1.9.0 with the client-side session module, the default signing key, and no session encryption. Production use of the default is called unsuitable by the advisory, but the affected condition still depends on application configuration.
Exploitation context
The advisory describes prerequisites: ability to write cookies, determine application startup time, and absence of encryption. CVE metadata marks the issue medium severity with local access and low privileges. KEV status is false, and the supplied sources provide no evidence of active exploitation.
Researcher notes
Key evidence is the GitHub advisory and linked source showing the default behavior. The vulnerable condition is configuration-sensitive: predictable signing key plus no encryption plus attacker cookie write capability. Avoid assuming all Ratpack applications are exploitable without confirming client-side session usage and defaults.
Mitigation direction
- Upgrade Ratpack to 1.9.0 or later where the default signing key is random.
- Supply a strong alternative signing key as recommended by Ratpack documentation.
- Enable client-side session encryption where the application design supports it.
- Check vendor guidance before choosing any non-documented compensating control.
Validation and detection
- Inventory services using ratpack/ratpack versions earlier than 1.9.0.
- Identify applications using the client-side session module.
- Review configuration for an explicit non-default signing key.
- Confirm whether client-side session encryption is enabled.
- Prioritize internet-facing or shared-host deployments for configuration review.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
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ATT&CK lookup starting points
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Open ATT&CK lookupCVE-2021-29480 mapping review
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Open ATT&CK lookup- Severity
- Medium
- CVSS
- 4.4 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N1.82.5Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
4.4MediumVector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/ratpack/ratpack/security/advisories/GHSA-2cc5-23r7-vc4vCVE reference · x_refsource_CONFIRM
- https://github.com/ratpack/ratpack/blob/29434f7ac6fd4b36a4495429b70f4c8163100332/ratpack-session/src/main/java/ratpack/session/clientside/ClientSideSessionConfig.java#L29CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Generation of Predictable Numbers or Identifiers
Generation of Predictable Numbers or Identifiers represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.