CVE-2026-34835
Fixed in a distro release EPSS <1%CVSS 4.8
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::Request parses the Host header using an AUTHORITY regular expression that accepts characters not permitted in RFC-compliant hostnames, including /, ?, #, and @. Because req.host returns the full parsed value, applications that validate hosts using naive prefix or suffix checks can be bypassed. This can lead to host header poisoning in applications that use req.host, req.url, or req.base_url for link generation, redirects, or origin validation. This issue has been patched in versions 3.1.21 and 3.2.6.
Products: Rack
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 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 | 1.5.2-3+deb8u3ubuntu1~esm11 |
| Ubuntu Pro 16.04 LTS | ruby-rack | 1.6.4-3ubuntu0.2+esm10 |
| Ubuntu Pro 18.04 LTS | ruby-rack | 1.6.4-4ubuntu0.2+esm10 |
| 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-9.3 | 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 |