CVSS 3.1
7.5 highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HCVE-2026-34230
High (7.5) in rack rack. EPSS 0.4% chance of exploitation in the next 30 days. Fixed in rack 2.2.23, 3.1.21, 3.2.6.
Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Utils.select_best_encoding processes Accept-Encoding values with quadratic time complexity when the header contains many wildcard (*) entries. Because this method is used by Rack::Deflater to choose a response encoding, an unauthenticated attacker can send a single request with a crafted Accept-Encoding header and cause disproportionate CPU consumption on the compression middleware path. This results in a denial of service condition for applications using Rack::Deflater. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.
Severity
- EPSS
- 0.4% chance of exploitation in the next 30 days; higher than 38% of CVEs (scores of 2026-10-31)
- CWEs
- CWE-400, CWE-407
- Published
- Modified
- Record from
- the NVD, synced
Affected
- rack:rack
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-v569-hp3g-36wr | RubyGems | rack | <2.2.23 | 2.2.23 |
| GHSA-v569-hp3g-36wr | RubyGems | rack | >=3.0.0.beta1 <3.1.21 | 3.1.21 |
| GHSA-v569-hp3g-36wr | RubyGems | rack | >=3.2.0 <3.2.6 | 3.2.6 |