{ "document": { "category": "csaf_base", "csaf_version": "2.0", "distribution": { "tlp": { "label": "WHITE" } }, "lang": "en", "notes": [ { "category": "legal_disclaimer", "text": "The Netherlands Cyber Security Center (henceforth: NCSC-NL) maintains this portal to enhance access to its information and vulnerabilities. The use of this information is subject to the following terms and conditions:\n\nThe vulnerabilities disclosed in this portal are gathered by NCSC-NL from a variety of open sources, which the user can retrieve from other platforms. NCSC-NL makes every reasonable effort to ensure that the content of this portal is kept up to date, and that it is accurate and complete. Nevertheless, NCSC-NL cannot entirely rule out the possibility of errors, and therefore cannot give any warranty in respect of its completeness, accuracy or real-time keeping up-to-date. NCSC-NL does not control nor guarantee the accuracy, relevance, timeliness or completeness of information obtained from these external sources. The vulnerabilities disclosed in this portal are intended solely for the convenience of professional parties to take appropriate measures to manage the risks posed to the cybersecurity. No rights can be derived from the information provided therein.\n\nNCSC-NL and the Kingdom of the Netherlands assume no legal liability or responsibility for any damage resulting from either the use or inability of use of the vulnerabilities disclosed in this portal. This includes damage resulting from the inaccuracy of incompleteness of the information contained in it.\nThe information on this page is subject to Dutch law. All disputes related to or arising from the use of this portal regarding the disclosure of vulnerabilities will be submitted to the competent court in The Hague. This choice of means also applies to the court in summary proceedings." } ], "publisher": { "category": "coordinator", "contact_details": "cert@ncsc.nl", "name": "National Cyber Security Centre", "namespace": "https://www.ncsc.nl/" }, "title": "CVE-2026-34829", "tracking": { "current_release_date": "2026-04-03T15:38:21.820710Z", "generator": { "date": "2026-02-17T15:00:00Z", "engine": { "name": "V.E.L.M.A", "version": "1.7" } }, "id": "CVE-2026-34829", "initial_release_date": "2026-04-02T17:28:40.886461Z", "revision_history": [ { "date": "2026-04-02T17:28:40.886461Z", "number": "1", "summary": "CVE created.| Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (1).| CWES updated (1)." }, { "date": "2026-04-02T17:28:42.695755Z", "number": "2", "summary": "NCSC Score created." }, { "date": "2026-04-02T17:39:33.835901Z", "number": "3", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products connected (3).| References created (1).| CWES updated (1)." }, { "date": "2026-04-02T17:39:35.794299Z", "number": "4", "summary": "NCSC Score updated." }, { "date": "2026-04-02T18:47:59.032041Z", "number": "5", "summary": "Unknown change." }, { "date": "2026-04-02T20:52:57.551648Z", "number": "6", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (3).| CWES updated (1)." }, { "date": "2026-04-02T20:53:02.103467Z", "number": "7", "summary": "NCSC Score updated." }, { "date": "2026-04-03T00:44:12.671495Z", "number": "8", "summary": "Source created.| CVE status created. (valid)| Products connected (2)." }, { "date": "2026-04-03T00:44:16.705828Z", "number": "9", "summary": "NCSC Score updated." }, { "date": "2026-04-03T06:45:57.134080Z", "number": "10", "summary": "Description created for source." }, { "date": "2026-04-03T15:30:48.723297Z", "number": "11", "summary": "Source connected.| CVE status created. (valid)| EPSS created." }, { "date": "2026-04-03T15:30:52.548329Z", "number": "12", "summary": "NCSC Score updated." } ], "status": "interim", "version": "12" } }, "product_tree": { "branches": [ { "branches": [ { "branches": [ { "category": "product_version_range", "name": "vers:unknown/<2.2.23", "product": { "name": "vers:unknown/<2.2.23", "product_id": "CSAFPID-5985093" } }, { "category": "product_version_range", "name": "vers:unknown/>=3.0.0.beta1|<3.1.21", "product": { "name": "vers:unknown/>=3.0.0.beta1|<3.1.21", "product_id": "CSAFPID-5985094" } }, { "category": "product_version_range", "name": "vers:unknown/>=3.2.0|<3.2.6", "product": { "name": "vers:unknown/>=3.2.0|<3.2.6", "product_id": "CSAFPID-5985095" } } ], "category": "product_name", "name": "rack" } ], "category": "vendor", "name": "rack" }, { "branches": [ { "branches": [ { "branches": [ { "category": "product_version_range", "name": "vers:deb/unknown", "product": { "name": "vers:deb/unknown", "product_id": "CSAFPID-2065710" } } ], "category": "product_name", "name": "ruby-rack" } ], "category": "product_family", "name": "bookworm" }, { "branches": [ { "branches": [ { "category": "product_version_range", "name": "vers:deb/unknown", "product": { "name": "vers:deb/unknown", "product_id": "CSAFPID-2065711" } } ], "category": "product_name", "name": "ruby-rack" } ], "category": "product_family", "name": "bullseye" } ], "category": "vendor", "name": "Debian" } ] }, "vulnerabilities": [ { "cve": "CVE-2026-34829", "cwe": { "id": "CWE-770", "name": "Allocation of Resources Without Limits or Throttling" }, "notes": [ { "category": "description", "text": "Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Multipart::Parser only wraps the request body in a BoundedIO when CONTENT_LENGTH is present. When a multipart/form-data request is sent without a Content-Length header, such as with HTTP chunked transfer encoding, multipart parsing continues until end-of-stream with no total size limit. For file parts, the uploaded body is written directly to a temporary file on disk rather than being constrained by the buffered in-memory upload limit. An unauthenticated attacker can therefore stream an arbitrarily large multipart file upload and consume unbounded disk space. This results in a denial of service condition for Rack applications that accept multipart form data. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.", "title": "nvd - https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-34829" }, { "category": "description", "text": "Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Multipart::Parser only wraps the request body in a BoundedIO when CONTENT_LENGTH is present. When a multipart/form-data request is sent without a Content-Length header, such as with HTTP chunked transfer encoding, multipart parsing continues until end-of-stream with no total size limit. For file parts, the uploaded body is written directly to a temporary file on disk rather than being constrained by the buffered in-memory upload limit. An unauthenticated attacker can therefore stream an arbitrarily large multipart file upload and consume unbounded disk space. This results in a denial of service condition for Rack applications that accept multipart form data. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.", "title": "cveprojectv5 - https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/34xxx/CVE-2026-34829.json" }, { "category": "description", "text": "## Summary\n\n`Rack::Multipart::Parser` only wraps the request body in a `BoundedIO` when `CONTENT_LENGTH` is present. When a `multipart/form-data` request is sent without a `Content-Length` header, such as with HTTP chunked transfer encoding, multipart parsing continues until end-of-stream with no total size limit.\n\nFor file parts, the uploaded body is written directly to a temporary file on disk rather than being constrained by the buffered in-memory upload limit. An unauthenticated attacker can therefore stream an arbitrarily large multipart file upload and consume unbounded disk space.\n\nThis results in a denial of service condition for Rack applications that accept multipart form data.\n\n## Details\n\n`Rack::Multipart::Parser.parse` applies `BoundedIO` only when `content_length` is not `nil`:\n\n```ruby\nio = BoundedIO.new(io, content_length) if content_length\n```\n\nWhen `CONTENT_LENGTH` is absent, the parser reads the multipart body until EOF without a global byte limit.\n\nAlthough Rack enforces `BUFFERED_UPLOAD_BYTESIZE_LIMIT` for retained non-file parts, file uploads are handled differently. When a multipart part includes a filename, the body is streamed to a `Tempfile`, and the retained-size accounting is not applied to that file content. As a result, file parts are not subject to the same upload size bound.\n\nAn attacker can exploit this by sending a chunked `multipart/form-data` request containing a file part and continuously streaming data without declaring a `Content-Length`. Rack will continue writing the uploaded data to disk until the client stops or the server exhausts available storage.\n\n## Impact\n\nAny Rack application that accepts `multipart/form-data` uploads may be affected if no upstream component enforces a request body size limit.\n\nAn unauthenticated attacker can send a large chunked file upload to consume disk space on the application host. This may cause request failures, application instability, or broader service disruption if the host runs out of available storage.\n\nThe practical impact depends on deployment architecture. Reverse proxies or application servers that enforce upload limits may reduce or eliminate exploitability, but Rack itself does not impose a total multipart upload limit in this code path when `CONTENT_LENGTH` is absent.\n\n## Mitigation\n\n* Update to a patched version of Rack that enforces a total multipart upload size limit even when `CONTENT_LENGTH` is absent.\n* Enforce request body size limits at the reverse proxy or application server.\n* Isolate temporary upload storage and monitor disk consumption for multipart endpoints.", "title": "github - https://api.github.com/advisories/GHSA-8vqr-qjwx-82mw" }, { "category": "description", "text": "Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Multipart::Parser only wraps the request body in a BoundedIO when CONTENT_LENGTH is present. When a multipart/form-data request is sent without a Content-Length header, such as with HTTP chunked transfer encoding, multipart parsing continues until end-of-stream with no total size limit. For file parts, the uploaded body is written directly to a temporary file on disk rather than being constrained by the buffered in-memory upload limit. An unauthenticated attacker can therefore stream an arbitrarily large multipart file upload and consume unbounded disk space. This results in a denial of service condition for Rack applications that accept multipart form data. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.", "title": "debian - https://security-tracker.debian.org/tracker/CVE-2026-34829" }, { "category": "other", "text": "0.00041", "title": "EPSS" }, { "category": "other", "text": "3.9", "title": "NCSC Score" }, { "category": "other", "text": "Is related to (a version of) an uncommon product", "title": "NCSC Score top decreasing factors" } ], "product_status": { "known_affected": [ "CSAFPID-5985093", "CSAFPID-5985094", "CSAFPID-5985095", "CSAFPID-2065710", "CSAFPID-2065711" ] }, "references": [ { "category": "external", "summary": "Source - nvd", "url": "https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-34829" }, { "category": "external", "summary": "Source - cveprojectv5", "url": "https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/34xxx/CVE-2026-34829.json" }, { "category": "external", "summary": "Source - github", "url": "https://api.github.com/advisories/GHSA-8vqr-qjwx-82mw" }, { "category": "external", "summary": "Source - debian", "url": "https://security-tracker.debian.org/tracker/CVE-2026-34829" }, { "category": "external", "summary": "Source - first", "url": "https://api.first.org/data/v1/epss?limit=10000&offset=0" }, { "category": "external", "summary": "Reference - cveprojectv5; github; nvd", "url": "https://github.com/rack/rack/security/advisories/GHSA-8vqr-qjwx-82mw" }, { "category": "external", "summary": "Reference - github", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-34829" }, { "category": "external", "summary": "Reference - github", "url": "https://github.com/advisories/GHSA-8vqr-qjwx-82mw" } ], "scores": [ { "cvss_v3": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH" }, "products": [ "CSAFPID-2065710", "CSAFPID-2065711", "CSAFPID-5985093", "CSAFPID-5985094", "CSAFPID-5985095" ] } ], "title": "CVE-2026-34829" } ] }