{"answers":{"affected":"4 open source packages ship an affected version, including rack. It affects 1 product.","exploited":"There is no known exploitation of CVE-2026-34835 in the wild and no public exploit code.","fix":"Upgrade rack to a fixed version for your release line: 3.1.21 or 3.2.6.","what":"CVE-2026-34835 is a medium-severity vulnerability in rack, published on 2 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-34835 and fix it if it is affected.\n\nWhat it is: CVE-2026-34835 is a medium-severity vulnerability in rack, published on 2 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-34835 in the wild and no public exploit code.\n\nAffected packages and fixed versions:\n- rack (RubyGems): affected from 3.0.0.beta1; fixed in 3.1.21\n- rack (RubyGems): affected from 3.0.0.beta1; fixed in 3.1.21\n- rack (RubyGems): affected from 3.2.0; fixed in 3.2.6\n- rack (RubyGems): affected from 3.2.0; fixed in 3.2.6\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-34835/ (Markdown: https://insights.sbomify.com/CVE-2026-34835/index.md)","id":"CVE-2026-34835","markdown":"https://insights.sbomify.com/CVE-2026-34835/index.md","name":"CVE-2026-34835","record":{"aliases":["DEBIAN-CVE-2026-34835","GHSA-g2pf-xv49-m2h5","MINI-2wff-rm7x-5hhg","MINI-2x4c-p5cr-7823","MINI-522x-4979-h862","MINI-5jgj-hqwr-mr89","MINI-c78r-gmcp-8jg2","MINI-fxmj-rmp7-gw8q","MINI-gq8r-2hf7-9q77","MINI-pfq4-7ghw-xf4m","MINI-pm4q-29rm-x2vc","MINI-rfg4-7hqj-6mwx","MINI-xfmq-xc9c-v4wf","UBUNTU-CVE-2026-34835"],"analysis":{"component_type":"library","fix_type":"upgrade","impacts":["security_bypass"],"network_reachable":"yes","non_default_config":false,"product_category":"Ruby web server interface","requires_auth":"none","summary":"Attackers can bypass host allowlists in Rack applications by sending invalid Host header characters, potentially enabling host header poisoning.","user_interaction":"not_required","vuln_class":"security_feature_bypass"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"GitHub_M","cpe":[{"product":"rack","vendor":"rack"}],"cvss":{"score":4.8,"severity":"medium","source":"cna","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","version":"3.1"},"cwes":[{"id":"CWE-1286","name":"Improper Validation of Syntactic Correctness of Input"}],"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.","ecosystems":["RubyGems"],"exploits":{"exploitdb":0,"first_seen":"2026-07-03","github_poc":1,"max_poc_stars":6,"metasploit":0,"nuclei":0,"refs":[{"date":"2026-07-03T02:50:25Z","kind":"github_poc","ref":"https://github.com/Cyber-note/CVE-2026-34835-Black-box-Analysis","stars":6,"title":"A black-box (DAST) security analysis of CVE-2026-34835 focusing on external validation methodology, observable behavior, security impact, and defensive recommendations."}],"tier":"poc_unverified"},"has_fix":true,"headline":"Rack: `Rack::Request` accepts invalid Host characters, enabling host allowlist bypass.","id":"CVE-2026-34835","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"RubyGems","product":null,"products":[],"type":"security_feature_bypass","year":"2026"},"n_packages":4,"n_references":1,"next":{"headline":"Combodo iTop: Improper access control in ajax.render.php and ajax.document.php","id":"CVE-2026-34836"},"packages":[{"ecosystem":"RubyGems","fixed":["3.1.21"],"introduced":["3.0.0.beta1"],"last_affected":[],"package":"rack","purl":null,"source":"GHSA-g2pf-xv49-m2h5"},{"ecosystem":"RubyGems","fixed":["3.1.21"],"introduced":["3.0.0.beta1"],"last_affected":[],"package":"rack","purl":"pkg:gem/rack","source":"GHSA-g2pf-xv49-m2h5"},{"ecosystem":"RubyGems","fixed":["3.2.6"],"introduced":["3.2.0"],"last_affected":[],"package":"rack","purl":null,"source":"GHSA-g2pf-xv49-m2h5"},{"ecosystem":"RubyGems","fixed":["3.2.6"],"introduced":["3.2.0"],"last_affected":[],"package":"rack","purl":"pkg:gem/rack","source":"GHSA-g2pf-xv49-m2h5"}],"prev":{"headline":"Bulwark Webmail: Authentication Bypass in verifyIdentity() due to missing cookie validation","id":"CVE-2026-34834"},"products":["rack"],"published":"2026-04-02","related":[{"cvss_score":7.5,"headline":"Rack: Local file inclusion in `Rack::Static` via URL Prefix Matching","id":"CVE-2026-34785","kev_date_added":null,"published":"2026-04-02"},{"cvss_score":7.5,"headline":"Rack: Algorithmic-Complexity DoS in Rack::Multipart::Parser","id":"CVE-2026-34827","kev_date_added":null,"published":"2026-04-02"},{"cvss_score":7.5,"headline":"Rack: Denial of Service via Unbounded Multipart File Upload Without Content-Length","id":"CVE-2026-34829","kev_date_added":null,"published":"2026-04-02"},{"cvss_score":7.5,"headline":"Rack has a Directory Traversal via Rack:Directory","id":"CVE-2026-22860","kev_date_added":null,"published":"2026-02-18"},{"cvss_score":7.5,"headline":"Rack is vulnerable to a memory-exhaustion DoS through unbounded URL-encoded body parsing","id":"CVE-2025-61919","kev_date_added":null,"published":"2025-10-10"},{"cvss_score":7.5,"headline":"Rack's unbounded multipart preamble buffering enables DoS (memory exhaustion)","id":"CVE-2025-61770","kev_date_added":null,"published":"2025-10-07"},{"cvss_score":7.5,"headline":"Rack's multipart parser buffers large non‑file fields entirely in memory, enabling DoS (memory exhaustion)","id":"CVE-2025-61771","kev_date_added":null,"published":"2025-10-07"}],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"CC BY 4.0","name":"GitHub Advisory Database","prefix":"GHSA"},{"class":"attribution","licence":"US public information, NVD API terms","name":"NVD"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"},{"class":"open","licence":"CC0","name":"PoC-in-GitHub"}],"ssvc":{"automatable":"no","exploitation":"none","technical_impact":"partial"},"state":"PUBLISHED","updated":"2026-04-02","vendors":["rack"]},"summary":"Attackers can bypass host allowlists in Rack applications by sending invalid Host header characters, potentially enabling host header poisoning.","url":"https://insights.sbomify.com/CVE-2026-34835/"}