{"id":"CVE-2026-34835","aliases":["DEBIAN-CVE-2026-34835","EUVD-2026-18478","GHSA-g2pf-xv49-m2h5","MGASA-2026-0226","UBUNTU-CVE-2026-34835","USN-8989-1"],"status":"published","title":"Rack: `Rack::Request` accepts invalid Host characters, enabling host allowlist bypass.","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.","severity":{"version":"3.1","score":4.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.002,"percentile":0.09894,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":true,"fix_available":true},"cwes":["CWE-1286"],"published":"2026-04-02T17:09:07Z","modified":"2026-11-04T03:43:07Z","exploits":[{"source":"pocgithub","id":"Cyber-note/CVE-2026-34835-Black-box-Analysis","title":"Cyber-note/CVE-2026-34835-Black-box-Analysis","date":"2026-07-03","url":"https://github.com/Cyber-note/CVE-2026-34835-Black-box-Analysis"}],"fixes":[{"ecosystem":"RubyGems","package":"rack","fixed_in":["3.1.21","3.2.6"],"sources":["ghsa","osv"]},{"ecosystem":"Debian:13","package":"ruby-rack","fixed_in":["3.1.20-0+deb13u2"],"sources":["osv"]},{"ecosystem":"Debian:14","package":"ruby-rack","fixed_in":["3.2.6-2"],"sources":["osv"]},{"ecosystem":"Ubuntu:25.10","package":"ruby-rack","fixed_in":["3.1.16-0.1ubuntu0.3"],"sources":["osv"]},{"ecosystem":"Ubuntu:26.04:LTS","package":"ruby-rack","fixed_in":["3.2.4-1ubuntu1.1"],"sources":["osv"]}],"affected":[{"source":"ghsa","ecosystem":"RubyGems","package":"rack","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.0.0.beta1"},{"fixed":"3.1.21"}]}]},{"source":"ghsa","ecosystem":"RubyGems","package":"rack","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.2.0"},{"fixed":"3.2.6"}]}]},{"source":"osv","ecosystem":"Debian:13","package":"ruby-rack","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.1.20-0+deb13u2"}]}],"versions":["3.1.16-0.1","3.1.18-1","3.1.18-1~deb13u1","3.1.20-0+deb13u1"]},{"source":"osv","ecosystem":"Debian:14","package":"ruby-rack","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.2.6-2"}]}],"versions":["3.1.16-0.1","3.1.18-1","3.1.18-1~deb13u1","3.2.4-1","3.2.5-1","3.2.5-2","3.2.6-1"]},{"source":"osv","ecosystem":"RubyGems","package":"rack","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.0.0.beta1"},{"fixed":"3.1.21"}]}],"versions":["3.0.0","3.0.0.beta1","3.0.0.rc1","3.0.1","3.0.10","3.0.11","3.0.12","3.0.13","3.0.14","3.0.15","3.0.16","3.0.17","3.0.18","3.0.2","3.0.3","3.0.4","3.0.4.1","3.0.4.2","3.0.5","3.0.6","3.0.6.1","3.0.7","3.0.8","3.0.9","3.0.9.1","3.1.0","3.1.1","3.1.10","3.1.11","3.1.12","3.1.13","3.1.14","3.1.15","3.1.16","3.1.17","3.1.18","3.1.19","3.1.2","3.1.20","3.1.3","3.1.4","3.1.5","3.1.6","3.1.7","3.1.8","3.1.9"]},{"source":"osv","ecosystem":"RubyGems","package":"rack","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.2.0"},{"fixed":"3.2.6"}]}],"versions":["3.2.0","3.2.1","3.2.2","3.2.3","3.2.4","3.2.5"]},{"source":"osv","ecosystem":"Mageia:9","package":"ruby-rack","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.2.23-1.mga9"}]}],"bundled":12},{"source":"osv","ecosystem":"Ubuntu:25.10","package":"ruby-rack","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.1.16-0.1ubuntu0.3"}]}],"versions":["2.2.7-1.1","3.1.16-0.1","3.1.16-0.1ubuntu0.1","3.1.16-0.1ubuntu0.2"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"ruby-rack","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.2.4-1ubuntu1.1"}]}],"versions":["3.1.16-0.1","3.1.18-1","3.1.18-1build1","3.2.4-1ubuntu1"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"ruby-rack","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.2.4-1ubuntu1.1"}]}],"versions":["3.1.16-0.1","3.1.18-1","3.1.18-1build1","3.2.4-1ubuntu1"],"bundled":13}],"products":[{"vendor":"rack","product":"rack"}],"references":[{"url":"https://github.com/rack/rack/security/advisories/GHSA-g2pf-xv49-m2h5","tags":["x_refsource_CONFIRM","Exploit","Mitigation","Vendor Advisory","advisory","web","report"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-34835","tags":["advisory"]},{"url":"https://github.com/rubysec/ruby-advisory-db/blob/master/gems/rack/CVE-2026-34835.yml","tags":["web"]},{"url":"https://github.com/advisories/GHSA-g2pf-xv49-m2h5"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34835.json","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-34835","tags":["advisory"]},{"url":"https://github.com/rack/rack","tags":["package"]},{"url":"https://advisories.mageia.org/MGASA-2026-0226.html","tags":["advisory"]},{"url":"https://bugs.mageia.org/show_bug.cgi?id=35446","tags":["report"]},{"url":"https://github.com/rack/rack/security/advisories/GHSA-vgpv-f759-9wx3","tags":["advisory"]},{"url":"https://github.com/rack/rack/security/advisories/GHSA-qfgr-crr9-7r49","tags":["advisory"]},{"url":"https://github.com/rack/rack/security/advisories/GHSA-v569-hp3g-36wr","tags":["advisory"]},{"url":"https://github.com/rack/rack/security/advisories/GHSA-7mqq-6cf9-v2qp","tags":["advisory"]},{"url":"https://github.com/rack/rack/security/advisories/GHSA-h2jq-g4cq-5ppq","tags":["advisory"]},{"url":"https://github.com/rack/rack/security/advisories/GHSA-q4qf-9j86-f5mh","tags":["advisory"]},{"url":"https://github.com/rack/rack/security/advisories/GHSA-x8cg-fq8g-mxfx","tags":["advisory"]},{"url":"https://github.com/rack/rack/security/advisories/GHSA-v6x5-cg8r-vv6x","tags":["advisory"]},{"url":"https://github.com/rack/rack/security/advisories/GHSA-8vqr-qjwx-82mw","tags":["advisory"]},{"url":"https://github.com/rack/rack/security/advisories/GHSA-qv7j-4883-hwh7","tags":["advisory"]},{"url":"https://github.com/rack/rack/security/advisories/GHSA-q2ww-5357-x388","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-34835","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-34835","tags":["report"]},{"url":"https://ubuntu.com/security/notices/USN-8182-1","tags":["advisory"]},{"url":"https://ubuntu.com/security/notices/USN-8989-1","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-26961","tags":["report"]},{"url":"https://ubuntu.com/security/CVE-2026-26962","tags":["report"]},{"url":"https://ubuntu.com/security/CVE-2026-32762","tags":["report"]},{"url":"https://ubuntu.com/security/CVE-2026-34230","tags":["report"]},{"url":"https://ubuntu.com/security/CVE-2026-34763","tags":["report"]},{"url":"https://ubuntu.com/security/CVE-2026-34785","tags":["report"]},{"url":"https://ubuntu.com/security/CVE-2026-34786","tags":["report"]},{"url":"https://ubuntu.com/security/CVE-2026-34826","tags":["report"]},{"url":"https://ubuntu.com/security/CVE-2026-34827","tags":["report"]},{"url":"https://ubuntu.com/security/CVE-2026-34829","tags":["report"]},{"url":"https://ubuntu.com/security/CVE-2026-34830","tags":["report"]},{"url":"https://ubuntu.com/security/CVE-2026-34831","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-34835","title":"Rack: `Rack::Request` accepts invalid Host characters, enabling host allowlist bypass.","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.","status":"published","published":"2026-04-02T17:09:07.047Z","modified":"2026-04-02T17:44:03.453Z","cvss":[{"version":"3.1","score":4.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium","assessor":"cna"}],"cwes":["CWE-1286"],"updated_at":"2026-11-02T14:20:13.962274Z"}],"euvd":[{"id":"EUVD-2026-18478","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.","status":"published","published":"2026-04-02T17:09:07Z","modified":"2026-04-02T17:44:03Z","cvss":[{"version":"3.1","score":4.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium"}],"updated_at":"2026-11-02T19:25:22.606516Z"}],"ghsa":[{"id":"GHSA-g2pf-xv49-m2h5","title":"Rack::Request accepts invalid Host characters, enabling host allowlist bypass","description":"## Summary\n\n`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.\n\nFor example, a check such as `req.host.start_with?(\"myapp.com\")` can be bypassed with `Host: myapp.com@evil.com`, and a check such as `req.host.end_with?(\"myapp.com\")` can be bypassed with `Host: evil.com/myapp.com`.\n\nThis 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.\n\n## Details\n\n`Rack::Request` parses the authority component using logic equivalent to:\n\n```ruby\nAUTHORITY = /\n  \\A\n  (?\u003chost\u003e\n    \\[(?\u003caddress\u003e#{ipv6})\\]\n    |\n    (?\u003caddress\u003e[[[:graph:]\u0026\u0026[^\\[\\]]]]*?)\n  )\n  (:(?\u003cport\u003e\\d+))?\n  \\z\n/x\n```\n\nThe character class used for non-IPv6 hosts accepts nearly all printable characters except `[` and `]`. This includes reserved URI delimiters such as `@`, `/`, `?`, and `#`, which are not valid hostname characters under RFC 3986 host syntax.\n\nAs a result, values such as the following are accepted and returned through `req.host`:\n\n```text\nmyapp.com@evil.com\nevil.com/myapp.com\nevil.com#myapp.com\n```\n\nApplications that attempt to allowlist hosts using string prefix or suffix checks may therefore treat attacker-controlled hosts as trusted. For example:\n\n```ruby\nreq.host.start_with?(\"myapp.com\")\n```\n\naccepts:\n\n```text\nmyapp.com@evil.com\n```\n\nand:\n\n```ruby\nreq.host.end_with?(\"myapp.com\")\n```\n\naccepts:\n\n```text\nevil.com/myapp.com\n```\n\nWhen those values are later used to build absolute URLs or enforce origin restrictions, the application may produce attacker-controlled results.\n\n## Impact\n\nApplications that rely on `req.host`, `req.url`, or `req.base_url` may be affected if they perform naive host validation or assume Rack only returns RFC-valid hostnames.\n\nIn affected deployments, an attacker may be able to bypass host allowlists and poison generated links, redirects, or origin-dependent security decisions. This can enable attacks such as password reset link poisoning or other host header injection issues.\n\nThe practical impact depends on application behavior. If the application or reverse proxy already enforces strict host validation, exploitability may be reduced or eliminated.\n\n## Mitigation\n\n* Update to a patched version of Rack that rejects invalid authority characters in `Host`.\n* Enforce strict `Host` header validation at the reverse proxy or load balancer.\n* Do not rely on prefix or suffix string checks such as `start_with?` or `end_with?` for host allowlisting.\n* Use exact host allowlists, or exact subdomain boundary checks, after validating that the host is syntactically valid.","status":"published","published":"2026-04-02T20:36:40Z","modified":"2026-05-13T16:19:23Z","cvss":[{"version":"3.1","score":4.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-1286"],"updated_at":"2026-11-02T14:40:08.003212Z"}],"nvd":[{"id":"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.","status":"published","published":"2026-04-02T18:16:33.967Z","modified":"2026-07-24T21:10:00.143Z","cvss":[{"version":"3.1","score":4.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium","assessor":"secondary"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium","assessor":"primary"}],"cwes":["CWE-1286"],"updated_at":"2026-11-02T14:12:12.73929Z"}],"osv":[{"id":"CVE-2026-34835","title":"Rack: `Rack::Request` accepts invalid Host characters, enabling host allowlist bypass.","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.","status":"published","published":"2026-04-02T17:09:07.047Z","modified":"2026-10-28T02:31:14.13410621Z","cvss":[{"version":"3.1","score":4.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-1286"],"updated_at":"2026-11-02T15:45:02.673625Z"},{"id":"DEBIAN-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.","status":"published","published":"2026-04-02T18:16:33.967Z","modified":"2026-10-01T03:03:22.2230009Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium"}],"updated_at":"2026-11-02T15:45:54.587575Z"},{"id":"GHSA-g2pf-xv49-m2h5","title":"Rack::Request accepts invalid Host characters, enabling host allowlist bypass","description":"## Summary\n\n`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.\n\nFor example, a check such as `req.host.start_with?(\"myapp.com\")` can be bypassed with `Host: myapp.com@evil.com`, and a check such as `req.host.end_with?(\"myapp.com\")` can be bypassed with `Host: evil.com/myapp.com`.\n\nThis 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.\n\n## Details\n\n`Rack::Request` parses the authority component using logic equivalent to:\n\n```ruby\nAUTHORITY = /\n  \\A\n  (?\u003chost\u003e\n    \\[(?\u003caddress\u003e#{ipv6})\\]\n    |\n    (?\u003caddress\u003e[[[:graph:]\u0026\u0026[^\\[\\]]]]*?)\n  )\n  (:(?\u003cport\u003e\\d+))?\n  \\z\n/x\n```\n\nThe character class used for non-IPv6 hosts accepts nearly all printable characters except `[` and `]`. This includes reserved URI delimiters such as `@`, `/`, `?`, and `#`, which are not valid hostname characters under RFC 3986 host syntax.\n\nAs a result, values such as the following are accepted and returned through `req.host`:\n\n```text\nmyapp.com@evil.com\nevil.com/myapp.com\nevil.com#myapp.com\n```\n\nApplications that attempt to allowlist hosts using string prefix or suffix checks may therefore treat attacker-controlled hosts as trusted. For example:\n\n```ruby\nreq.host.start_with?(\"myapp.com\")\n```\n\naccepts:\n\n```text\nmyapp.com@evil.com\n```\n\nand:\n\n```ruby\nreq.host.end_with?(\"myapp.com\")\n```\n\naccepts:\n\n```text\nevil.com/myapp.com\n```\n\nWhen those values are later used to build absolute URLs or enforce origin restrictions, the application may produce attacker-controlled results.\n\n## Impact\n\nApplications that rely on `req.host`, `req.url`, or `req.base_url` may be affected if they perform naive host validation or assume Rack only returns RFC-valid hostnames.\n\nIn affected deployments, an attacker may be able to bypass host allowlists and poison generated links, redirects, or origin-dependent security decisions. This can enable attacks such as password reset link poisoning or other host header injection issues.\n\nThe practical impact depends on application behavior. If the application or reverse proxy already enforces strict host validation, exploitability may be reduced or eliminated.\n\n## Mitigation\n\n* Update to a patched version of Rack that rejects invalid authority characters in `Host`.\n* Enforce strict `Host` header validation at the reverse proxy or load balancer.\n* Do not rely on prefix or suffix string checks such as `start_with?` or `end_with?` for host allowlisting.\n* Use exact host allowlists, or exact subdomain boundary checks, after validating that the host is syntactically valid.","status":"published","published":"2026-04-02T20:36:40Z","modified":"2026-09-10T03:50:44.295660719Z","cvss":[{"version":"3.1","score":4.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-1286"],"updated_at":"2026-11-02T15:46:47.119724Z"},{"id":"UBUNTU-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.","status":"published","published":"2026-04-02T18:16:00Z","modified":"2026-11-04T03:42:05.029623401Z","cvss":[{"version":"3.1","score":4.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium"}],"updated_at":"2026-11-04T03:56:18.279609Z"},{"id":"MGASA-2026-0226","title":"Updated ruby-rack packages fix security vulnerabilities","description":"CVE-2026-26961 Greedy multipart boundary parsing can cause parser\ndifferentials and WAF bypass. `Forwarded` header semicolon injection\nenables `Host` and `Scheme` spoofing.\nCVE-2026-34230 Quadratic complexity in\n`Rack::Utils.select_best_encoding` via wildcard `Accept-Encoding`\nheader.\nCVE-2026-34763 Root directory disclosure via unescaped regex\ninterpolation in `Rack::Directory`.\nCVE-2026-34785 `Rack::Static` prefix matching can expose unintended\nfiles under the static root.\nCVE-2026-34786 `Rack::Static` `header_rules` bypass via URL-encoded path\nmismatch.\nCVE-2026-34826 Multipart byte range processing allows denial of service\nvia excessive overlapping ranges.\nCVE-2026-34827 Multipart header parsing allows denial of service via\nescape-heavy quoted parameters.\nCVE-2026-34829 Multipart parsing without `Content-Length` header allows\nunbounded chunked file uploads.\nCVE-2026-34830 `Rack::Sendfile` header-based `X-Accel-Mapping` regex\ninjection enables unauthorized `X-Accel-Redirect`.\nCVE-2026-34831 `Content-Length` mismatch in `Rack::Files` error\nresponses.\nCVE-2026-34835 `Rack::Request` accepts invalid Host characters, enabling\nhost allowlist bypass.\n","status":"published","published":"2026-06-18T21:28:22Z","modified":"2026-06-18T21:30:04.563755676Z","updated_at":"2026-11-02T15:49:43.795591Z"},{"id":"USN-8989-1","title":"ruby-rack vulnerabilities","description":"Andrew Lacambra discovered that Rack did not properly parse certain regular\nexpressions. An attacker could possibly use this issue to bypass network\nsecurity filters. (CVE-2026-26961)\n\nWilliam T. Nelson discovered that Rack did not handle multipart headers\ncorrectly. An attacker could possibly use this issue to cause downstream\nparsing issues or a denial of service. (CVE-2026-26962)\n\nIt was discovered that Rack did not handle the Forwarded header correctly.\nAn attacker could possibly use this issue to manipulate header values.\n(CVE-2026-32762)\n\nIt was discovered that Rack could consume excessive CPU when handling\ncertain Accept-Encoding values. An attacker could possibly use this issue\nto cause a denial of service. (CVE-2026-34230)\n\nHaruki Oyama discovered that certain configurations of Rack could\nerroneously fail to derive the displayed directory path, and expose the\nfull file system path. An attacker could possibly use this issue to\ndisclose deployment details such as layout and usernames. (CVE-2026-34763)\n\nIt was discovered that Rack did not properly handle static file paths. An\nattacker could possibly use this issue to exfiltrate unintentionally served\ndata. (CVE-2026-34785)\n\nHaruki Oyama discovered that Rack did not apply header rules to certain\nrequests for URL-encoded static paths. An attacker could possibly use this\nissue to bypass security-relevant response headers. (CVE-2026-34786)\n\nIt was discovered that Rack did not limit the number of ranges requested in\nthe Range header. An attacker could possibly use this issue to cause a\ndenial of service. (CVE-2026-34826)\n\nIt was discovered that Rack could consume excessive CPU when parsing\ncertain multipart parameters. An attacker could possibly use this issue to\ncause a denial of service. (CVE-2026-34827)\n\nIt was discovered that Rack could consume unbounded disk space when\nhandling requests without a Content-Length header. An attacker could\npossibly use this issue to cause a denial of service. (CVE-2026-34829)\n\nMehtab Zafar discovered that Rack directly interpreted the X-Accel-Mapping\nheader as a regular expression without escaping. An attacker could possibly\nuse this issue to exfiltrate arbitrary files from internal locations.\n(CVE-2026-34830)\n\nIt was discovered that Rack did not properly handle messages with Unicode.\nAn attacker could possibly use this issue to cause a denial of service.\n(CVE-2026-34831)\n\nIt was discovered that Rack did not properly parse the Host header. An\nattacker could possibly use this issue to bypass security filters or poison\ngenerated links. (CVE-2026-34835)","status":"published","published":"2026-11-03T17:12:03Z","modified":"2026-11-04T03:43:07.892494882Z","updated_at":"2026-11-04T03:56:18.279609Z"}]}}