CVE-2026-34835
Description
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.
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Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
rackRubyGems | >= 3.0.0.beta1, < 3.1.21 | 3.1.21 |
rackRubyGems | >= 3.2.0, < 3.2.6 | 3.2.6 |
Affected products
38- osv-coords37 versionspkg:apk/chainguard/kube-fluentd-operatorpkg:apk/chainguard/logstash-8.19pkg:apk/chainguard/logstash-8.19-iamguarded-compatpkg:apk/chainguard/logstash-8.19-with-output-opensearchpkg:apk/chainguard/logstash-9.0pkg:apk/chainguard/logstash-9.0-iamguarded-compatpkg:apk/chainguard/logstash-9.0-with-output-opensearchpkg:apk/chainguard/logstash-9.1pkg:apk/chainguard/logstash-9.1-bitnami-compatpkg:apk/chainguard/logstash-9.1-iamguarded-compatpkg:apk/chainguard/logstash-9.1-with-output-opensearchpkg:apk/chainguard/logstash-9.2pkg:apk/chainguard/logstash-9.2-iamguarded-compatpkg:apk/chainguard/logstash-9.2-with-output-opensearchpkg:apk/chainguard/logstash-9.3pkg:apk/chainguard/logstash-9.3-iamguarded-compatpkg:apk/chainguard/logstash-9.3-with-output-opensearchpkg:apk/chainguard/pact-broker-dockerpkg:apk/chainguard/pact-broker-docker-fipspkg:apk/chainguard/ruby3.2-rails-7.2pkg:apk/chainguard/ruby3.2-rails-8.0pkg:apk/chainguard/ruby3.4-rails-7.2pkg:apk/chainguard/ruby3.4-rails-8.0pkg:apk/wolfi/kube-fluentd-operatorpkg:apk/wolfi/logstash-9.1pkg:apk/wolfi/logstash-9.1-bitnami-compatpkg:apk/wolfi/logstash-9.1-iamguarded-compatpkg:apk/wolfi/logstash-9.1-with-output-opensearchpkg:apk/wolfi/logstash-9.2pkg:apk/wolfi/logstash-9.2-iamguarded-compatpkg:apk/wolfi/logstash-9.2-with-output-opensearchpkg:apk/wolfi/logstash-9.3pkg:apk/wolfi/logstash-9.3-iamguarded-compatpkg:apk/wolfi/logstash-9.3-with-output-opensearchpkg:apk/wolfi/ruby3.2-rails-8.0pkg:apk/wolfi/ruby3.4-rails-8.0pkg:gem/rack
< 1.18.2-r67+ 36 more
- (no CPE)range: < 1.18.2-r67
- (no CPE)range: < 8.19.14-r3
- (no CPE)range: < 8.19.14-r3
- (no CPE)range: < 8.19.14-r3
- (no CPE)range: < 9.0.8-r20
- (no CPE)range: < 9.0.8-r20
- (no CPE)range: < 9.0.8-r20
- (no CPE)range: < 9.1.10-r6
- (no CPE)range: < 9.1.10-r6
- (no CPE)range: < 9.1.10-r6
- (no CPE)range: < 9.1.10-r6
- (no CPE)range: < 9.2.8-r2
- (no CPE)range: < 9.2.8-r2
- (no CPE)range: < 9.2.8-r2
- (no CPE)range: < 9.3.3-r2
- (no CPE)range: < 9.3.3-r2
- (no CPE)range: < 9.3.3-r2
- (no CPE)range: < 2.137.0.2.118.0-r4
- (no CPE)range: < 2.137.0.2.118.0-r2
- (no CPE)range: < 7.2.3.1-r2
- (no CPE)range: < 8.0.5-r0
- (no CPE)range: < 7.2.3.1-r1
- (no CPE)range: < 8.0.5-r2
- (no CPE)range: < 1.18.2-r67
- (no CPE)range: < 9.1.10-r6
- (no CPE)range: < 9.1.10-r6
- (no CPE)range: < 9.1.10-r6
- (no CPE)range: < 9.1.10-r6
- (no CPE)range: < 9.2.8-r2
- (no CPE)range: < 9.2.8-r2
- (no CPE)range: < 9.2.8-r2
- (no CPE)range: < 9.3.3-r2
- (no CPE)range: < 9.3.3-r2
- (no CPE)range: < 9.3.3-r2
- (no CPE)range: < 8.0.5-r0
- (no CPE)range: < 8.0.5-r2
- (no CPE)range: >= 3.0.0.beta1, < 3.1.21
Patches
Vulnerability mechanics
References
4- github.com/advisories/GHSA-g2pf-xv49-m2h5ghsaADVISORY
- github.com/rack/rack/security/advisories/GHSA-g2pf-xv49-m2h5nvdVendor AdvisoryExploitMitigationWEB
- nvd.nist.gov/vuln/detail/CVE-2026-34835ghsaADVISORY
- github.com/rubysec/ruby-advisory-db/blob/master/gems/rack/CVE-2026-34835.ymlghsaWEB
News mentions
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