{"answers":{"affected":"6 open source packages ship an affected version, including rack. It affects 1 product.","exploited":"There is no known exploitation of CVE-2026-34831 in the wild and no public exploit code.","fix":"Upgrade rack to a fixed version for your release line: 2.2.23, 3.1.21 or 3.2.6.","what":"CVE-2026-34831 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-2026-34831 and fix it if it is affected.\n\nWhat it is: CVE-2026-34831 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-2026-34831 in the wild and no public exploit code.\n\nAffected packages and fixed versions:\n- rack (RubyGems): affected all versions; fixed in 2.2.23\n- rack (RubyGems): affected all versions; fixed in 2.2.23\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-2026-34831/ (Markdown: https://insights.sbomify.com/CVE-2026-34831/index.md)","id":"CVE-2026-34831","markdown":"https://insights.sbomify.com/CVE-2026-34831/index.md","name":"CVE-2026-34831","record":{"aliases":["DEBIAN-CVE-2026-34831","GHSA-q2ww-5357-x388","MINI-23x3-g4pr-hqx5","MINI-2vjr-2xj3-mp4g","MINI-373h-wh2v-6f8v","MINI-3vvp-422v-m53w","MINI-4fmr-pvhv-jw5w","MINI-6947-f25v-fq69","MINI-8jmc-7r46-9vp2","MINI-92gj-23rf-2pc6","MINI-f57v-92gx-fhqp","MINI-g4hg-r4mc-764p","MINI-mpxp-j4q8-8qm2","MINI-pfh4-5878-5fhj","MINI-pvv5-qwmr-83c2","MINI-px74-cjmj-frcq","MINI-qxxh-259f-3x2g","MINI-rfq3-f8h8-qcqc","MINI-rpvq-3x2x-mp7j","MINI-v2g5-47f4-9x65","MINI-v54w-fvgp-7hmx","MINI-vqw3-c26g-vxmh","MINI-w44m-9hfc-43wf","MINI-whh5-246c-r95c","MINI-x3xr-qqqr-4j4r","MINI-xvp4-cwjw-2v76","UBUNTU-CVE-2026-34831"],"analysis":{"component_type":"library","fix_type":"upgrade","impacts":["denial_of_service","other"],"network_reachable":"yes","non_default_config":false,"product_category":"Ruby web server interface","requires_auth":"none","summary":"An attacker can cause HTTP response desynchronization in Rack::Files by exploiting a Content-Length mismatch with multibyte UTF-8 characters in 404 responses.","user_interaction":"not_required","vuln_class":"other"},"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-135","name":"Incorrect Calculation of Multi-Byte String Length"},{"id":"CWE-130","name":"Improper Handling of Length Parameter Inconsistency"}],"description":"Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Files#fail sets the Content-Length response header using String#size instead of String#bytesize. When the response body contains multibyte UTF-8 characters, the declared Content-Length is smaller than the number of bytes actually sent on the wire. Because Rack::Files reflects the requested path in 404 responses, an attacker can trigger this mismatch by requesting a non-existent path containing percent-encoded UTF-8 characters. This results in incorrect HTTP response framing and may cause response desynchronization in deployments that rely on the incorrect Content-Length value. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.","ecosystems":["RubyGems"],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":true,"headline":"Rack: Content-Length mismatch in Rack::Files error responses","id":"CVE-2026-34831","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"RubyGems","product":null,"products":[],"type":"other","year":"2026"},"n_packages":6,"n_references":1,"next":{"headline":"Scoold: Cross-Account Feedback Deletion (IDOR)","id":"CVE-2026-34832"},"packages":[{"ecosystem":"RubyGems","fixed":["2.2.23"],"introduced":["0"],"last_affected":[],"package":"rack","purl":null,"source":"GHSA-q2ww-5357-x388"},{"ecosystem":"RubyGems","fixed":["2.2.23"],"introduced":["0"],"last_affected":[],"package":"rack","purl":"pkg:gem/rack","source":"GHSA-q2ww-5357-x388"},{"ecosystem":"RubyGems","fixed":["3.1.21"],"introduced":["3.0.0.beta1"],"last_affected":[],"package":"rack","purl":null,"source":"GHSA-q2ww-5357-x388"},{"ecosystem":"RubyGems","fixed":["3.1.21"],"introduced":["3.0.0.beta1"],"last_affected":[],"package":"rack","purl":"pkg:gem/rack","source":"GHSA-q2ww-5357-x388"},{"ecosystem":"RubyGems","fixed":["3.2.6"],"introduced":["3.2.0"],"last_affected":[],"package":"rack","purl":null,"source":"GHSA-q2ww-5357-x388"},{"ecosystem":"RubyGems","fixed":["3.2.6"],"introduced":["3.2.0"],"last_affected":[],"package":"rack","purl":"pkg:gem/rack","source":"GHSA-q2ww-5357-x388"}],"prev":{"headline":"Rack: Rack::Sendfile regex injection via HTTP_X_ACCEL_MAPPING header allows arbitrary file reads through nginx","id":"CVE-2026-34830"},"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)"}],"ssvc":{"automatable":"no","exploitation":"none","technical_impact":"partial"},"state":"PUBLISHED","updated":"2026-04-03","vendors":["rack"]},"summary":"An attacker can cause HTTP response desynchronization in Rack::Files by exploiting a Content-Length mismatch with multibyte UTF-8 characters in 404 responses.","url":"https://insights.sbomify.com/CVE-2026-34831/"}