Rack: Forwarded Header semicolon injection enables Host and Scheme spoofing
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- Low · Low · None
- Fix status
- Partial Red Hat: 6 without a fix
Attack profile from CVSS 3.1 · NVD. Fix status from CNA, GitHub and Red Hat.
Summary
Rack is a modular Ruby web server interface. From versions 3.0.0.beta1 to before 3.1.21 and 3.2.0 to before 3.2.6, Rack::Utils.forwarded_values parses the RFC 7239 Forwarded header by splitting on semicolons before handling quoted-string values. Because quoted values may legally contain semicolons, a header can be interpreted by Rack as multiple Forwarded directives rather than as a single quoted for value. In deployments where an upstream proxy, WAF, or intermediary validates or preserves quoted Forwarded values differently, this discrepancy can allow an attacker to smuggle host, proto, for, or by parameters through a single header value. This issue has been patched in versions 3.1.21 and 3.2.6.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| rack | rack | 3.0.0.beta1 to before 3.1.21; 3.2.0 to before 3.2.6 | 3.1.21, 3.2.6 | Patch available | CNA |
| — | rack (RubyGems) | 3.0.0.beta1 to before 3.1.21 | 3.1.21 | Patch available | GHSA-qfgr-crr9-7r49 |
| — | rack (RubyGems) | 3.2.0 to before 3.2.6 | 3.2.6 | Patch available | GHSA-qfgr-crr9-7r49 |
- rack Vendorrack Affected 3.0.0.beta1 to before 3.1.21; 3.2.0 to before 3.2.6 Fixed in 3.1.21, 3.2.6 Patch available CNA
- rack (RubyGems) Vendor— Affected 3.0.0.beta1 to before 3.1.21 Fixed in 3.1.21 Patch available GHSA-qfgr-crr9-7r49
- rack (RubyGems) Vendor— Affected 3.2.0 to before 3.2.6 Fixed in 3.2.6 Patch available GHSA-qfgr-crr9-7r49
Remediation
- Fix · CNA rack (rack) Fixed in 3.1.21, 3.2.6
- Fix · GHSA-qfgr-crr9-7r49 rack (RubyGems) Fixed in 3.1.21 Advisory →
- Fix · GHSA-qfgr-crr9-7r49 rack (RubyGems) Fixed in 3.2.6 Advisory →
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Logging Subsystem for Red Hat OpenShift | Affected | No fix yet: Fix deferred |
| Red Hat 3scale API Management Platform 2 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 10 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 7 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-02 Threatist record created from CVE-2026-32762
- 2026-10-03 Alias added: GHSA-qfgr-crr9-7r49
References
More Rack vulnerabilities
- TI-2024-16580 Rack ReDos in content type parsing (2nd degree polynomial) CVSS 3.1HIGH 7.5
- TI-2024-17236 Possible Denial of Service Vulnerability in Rack Header Parsing CVSS 3.1HIGH 7.5
- TI-2024-17231 Possible DoS Vulnerability with Range Header in Rack CVSS 3.1HIGH 7.5
- TI-2023-12254 Uncontrolled resource consumption in https://github.com/rack/rack CVSS 3.1HIGH 7.5
- TI-2025-38165 Rack's multipart parser buffers unbounded per-part headers, enabling DoS (memory exhaustion) CVSS 3.1HIGH 7.5
- TI-2025-38163 Rack's unbounded multipart preamble buffering enables DoS (memory exhaustion) CVSS 3.1HIGH 7.5
Sources
- CVE-2026-32762 · CVE Program
- CVE-2026-32762 · NVD
- FIRST EPSS
- GHSA-qfgr-crr9-7r49 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-32762 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences