Security readout for executives and security teams
Plain-English summary
CVE-2021-22902 affects Rails' actionpack request handling. A specially formed HTTP Accept header can make Rails spend excessive CPU parsing MIME types, causing denial of service. It is not described as data theft or code execution, but exposed Rails apps could lose availability until upgraded.
Executive priority
Schedule prompt remediation for exposed Rails applications. The primary business risk is service disruption, not compromise of confidentiality or integrity. Prioritize customer-facing and revenue-critical services first.
Technical view
Action Dispatch's MIME type parser in actionpack before 6.0.3.7 and 6.1.3.2 can trigger catastrophic regex backtracking when parsing crafted Accept headers. The CVE maps to CWE-400, uncontrolled resource consumption. The source bundle names fixed releases but provides no CVSS vector.
Likely exposure
Exposure is most likely in Rails applications using vulnerable actionpack versions and reachable over HTTP. Any public route processed by Action Dispatch may be relevant because the issue is in request header parsing, not a specific business endpoint.
Exploitation context
The provided sources describe crafted Accept headers causing denial of service. They do not show KEV listing, active exploitation, public weaponization, or observed attacks. Treat exploit prevalence as unproven from this bundle.
Researcher notes
Key uncertainty is severity scoring: the source bundle has no CVSS vector. The vulnerability class is regex-driven resource exhaustion in Action Dispatch MIME parsing, fixed in named Rails/actionpack releases. Avoid assuming endpoint-specific exposure without confirming request flow through vulnerable Rails code.
Mitigation direction
- Upgrade actionpack/Rails to 6.0.3.7, 6.1.3.2, or later supported releases.
- Check the official Rails advisory for branch-specific upgrade guidance.
- Prioritize internet-facing Rails services and high-availability applications.
- Use edge rate limiting or request filtering only as temporary defense-in-depth.
- Monitor application latency and CPU saturation after remediation.
Validation and detection
- Inventory Rails applications and record actionpack gem versions.
- Confirm production deployments are not running actionpack below fixed versions.
- Review dependency lockfiles and container images for vulnerable versions.
- Check web logs for repeated malformed Accept headers and matching latency spikes.
- Verify staging and production both use the patched dependency set.
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
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-400: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-22902 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
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 and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://hackerone.com/reports/1138654CVE reference · x_refsource_MISC
- https://discuss.rubyonrails.org/t/cve-2021-22902-possible-denial-of-service-vulnerability-in-action-dispatch/77866CVE 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.
Uncontrolled Resource Consumption
Uncontrolled Resource Consumption represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.