CVE-2026-34827
Fixed in a distro release EPSS <1%CVSS 7.5
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::Multipart::Parser#handle_mime_head parses quoted multipart parameters such as Content-Disposition: form-data; name="..." using repeated String#index searches combined with String#slice! prefix deletion. For escape-heavy quoted values, this causes super-linear processing. An unauthenticated attacker can send a crafted multipart/form-data request containing many parts with long backslash-escaped parameter values to trigger excessive CPU usage during multipart parsing. This results in a denial of service condition in Rack applications that accept multipart form data. This issue has been patched in versions 3.1.21 and 3.2.6.
Products: Rack, Logging Subsystem for Red Hat OpenShift, Red Hat 3scale API Management Platform 2, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9
Fixed upstream
| Ecosystem | Package | Fixed in |
|---|---|---|
| RubyGems | rack | 3.1.21 |
| RubyGems | rack | 3.2.6 |
Distro releases
| Release | Package | Fixed in |
|---|---|---|
| Chainguard | kube-fluentd-operator | 1.18.2-r60 |
| Chainguard | kube-fluentd-operator | 1.18.2-r67 |
| Chainguard | logstash-8.17 | no fix |
| Chainguard | logstash-8.17-iamguarded-compat | no fix |
| Chainguard | logstash-8.17-with-output-opensearch | no fix |
| Chainguard | logstash-8.18 | no fix |
| Chainguard | logstash-8.18-iamguarded-compat | no fix |
| Chainguard | logstash-8.18-with-output-opensearch | no fix |
| Chainguard | logstash-8.19 | 8.19.14-r3 |
| Chainguard | logstash-8.19-iamguarded-compat | 8.19.14-r3 |
| Chainguard | logstash-8.19-with-output-opensearch | 8.19.14-r3 |
| Chainguard | logstash-9.0 | 9.0.8-r20 |
| Chainguard | logstash-9.0-iamguarded-compat | 9.0.8-r20 |
| Chainguard | logstash-9.0-with-output-opensearch | 9.0.8-r20 |
| Chainguard | logstash-9.1 | 9.1.10-r6 |
| Chainguard | logstash-9.1-bitnami-compat | 9.1.10-r6 |
| Chainguard | logstash-9.1-iamguarded-compat | 9.1.10-r6 |
| Chainguard | logstash-9.1-with-output-opensearch | 9.1.10-r6 |
| Chainguard | logstash-9.2 | 9.2.8-r2 |
| Chainguard | logstash-9.2-iamguarded-compat | 9.2.8-r2 |
| Chainguard | logstash-9.2-with-output-opensearch | 9.2.8-r2 |
| Chainguard | logstash-9.3 | 9.3.3-r2 |
| Chainguard | logstash-9.3-iamguarded-compat | 9.3.3-r2 |
| Chainguard | logstash-9.3-with-output-opensearch | 9.3.3-r2 |
| Chainguard | pact-broker-docker | 2.137.0.2.118.0-r4 |
| Chainguard | pact-broker-docker-fips | 2.137.0.2.118.0-r2 |
| Chainguard | ruby3.2-rails-7.2 | 7.2.3.1-r1 |
| Chainguard | ruby3.2-rails-7.2 | 7.2.3.1-r2 |
| Chainguard | ruby3.2-rails-8.0 | 8.0.5-r0 |
| Chainguard | ruby3.4-rails-7.2 | 7.2.3.1-r1 |
| Chainguard | ruby3.4-rails-8.0 | 8.0.5-r1 |
| Chainguard | ruby3.4-rails-8.0 | 8.0.5-r2 |
| Debian 13 | ruby-rack | 3.1.20-0+deb13u2 |
| Debian 14 | ruby-rack | 3.2.6-2 |
| Ubuntu 22.04 LTS | ruby-rack | no fix |
| Ubuntu 24.04 LTS | ruby-rack | no fix |
| Ubuntu 24.04 LTS | ruby-rack | 2.2.7-1ubuntu0.7 |
| Ubuntu 25.10 | ruby-rack | 3.1.16-0.1ubuntu0.3 |
| Ubuntu 26.04 LTS | ruby-rack | no fix |
| Ubuntu Pro 14.04 LTS | ruby-rack | no fix |
| Ubuntu Pro 14.04 LTS | ruby-rack | 1.5.2-3+deb8u3ubuntu1~esm11 |
| Ubuntu Pro 16.04 LTS | ruby-rack | 1.6.4-3ubuntu0.2+esm10 |
| Ubuntu Pro 16.04 LTS | ruby-rack | no fix |
| Ubuntu Pro 18.04 LTS | ruby-rack | no fix |
| Ubuntu Pro 18.04 LTS | ruby-rack | 1.6.4-4ubuntu0.2+esm10 |
| Ubuntu Pro 20.04 LTS | ruby-rack | no fix |
| Ubuntu Pro 20.04 LTS | ruby-rack | 2.0.7-2ubuntu0.1+esm10 |
| Ubuntu Pro 22.04 LTS | ruby-rack | 2.1.4-5ubuntu1.2+esm3 |
| Wolfi | kube-fluentd-operator | 1.18.2-r60 |
| Wolfi | kube-fluentd-operator | 1.18.2-r67 |
| Wolfi | logstash-9.1 | 9.1.10-r6 |
| Wolfi | logstash-9.1-bitnami-compat | 9.1.10-r6 |
| Wolfi | logstash-9.1-iamguarded-compat | 9.1.10-r6 |
| Wolfi | logstash-9.1-with-output-opensearch | 9.1.10-r6 |
| Wolfi | logstash-9.2 | 9.2.8-r2 |
| Wolfi | logstash-9.2-iamguarded-compat | 9.2.8-r2 |
| Wolfi | logstash-9.2-with-output-opensearch | 9.2.8-r2 |
| Wolfi | logstash-9.3 | 9.3.3-r2 |
| Wolfi | logstash-9.3-iamguarded-compat | 9.3.3-r2 |
| Wolfi | logstash-9.3-with-output-opensearch | 9.3.3-r2 |
| Wolfi | ruby3.2-rails-8.0 | 8.0.5-r0 |
| Wolfi | ruby3.4-rails-8.0 | 8.0.5-r2 |