Rack Multiple Security Issues

Information disclosure in Rack web server interface (versions <2.2.23, <3.1.21, <3.2.6) allows unauthenticated remote attackers to access sensitive files due to flawed prefix matching in Rack::Static. The vulnerability enables access to unintended files sharing configured URL prefixes (e.g., '/css' matching '/css-backup.sql'), exposing configuration files, database backups, or environment variables. CVSS 7.5 (High) with network vector and no complexity. No public exploit identified at time of analysis.

Unbounded disk consumption in Rack's multipart parser allows remote denial of service when HTTP requests lack Content-Length headers. Rack versions prior to 2.2.23, 3.1.21, and 3.2.6 fail to enforce size limits on multipart/form-data uploads sent via chunked transfer encoding, enabling unauthenticated attackers to exhaust disk space by streaming arbitrarily large file uploads. CVSS 7.5 (High) reflects the network-accessible, low-complexity attack requiring no privileges. No public exploit identified at time of analysis, though the attack technique is well-understood.

Denial of service in Rack::Utils.select_best_encoding allows unauthenticated remote attackers to consume disproportionate CPU resources via a crafted Accept-Encoding header containing multiple wildcard entries, affecting Rack versions prior to 2.2.23, 3.1.21, and 3.2.6. The vulnerability exploits quadratic time complexity in the encoding selection algorithm used by Rack::Deflater middleware, enabling a single HTTP request to trigger sustained CPU exhaustion and application unavailability.

Denial of service in Rack versions prior to 2.2.23, 3.1.21, and 3.2.6 allows unauthenticated remote attackers to consume disproportionate CPU, memory, I/O, and bandwidth by supplying many small overlapping byte ranges in HTTP Range headers, bypassing the existing CVE-2024-26141 fix that only validates total byte coverage. The vulnerability affects Rack's file-serving paths that process multipart byte range responses, enabling attackers to degrade service availability with minimal request complexity.

Rack::Sendfile in versions prior to 2.2.23, 3.1.21, and 3.2.6 allows remote attackers to inject regex metacharacters into X-Accel-Mapping request headers, enabling unescaped interpolation that manipulates the X-Accel-Redirect response header and causes nginx to serve unintended files from internal locations. No public exploit code or active exploitation has been confirmed; patch versions are available from the vendor.

HTTP response desynchronization in Rack web server framework versions prior to 2.2.23, 3.1.21, and 3.2.6 allows remote attackers to cause Content-Length header mismatches by requesting non-existent paths with percent-encoded UTF-8 characters. The vulnerability stems from Rack::Files#fail using String#size instead of String#bytesize when setting Content-Length, causing declared header values to be smaller than actual bytes transmitted, potentially leading to response framing errors and information disclosure in deployments sensitive to Content-Length validation. No public exploit code or confirmed active exploitation identified at time of analysis.

Rack::Static fails to apply security-relevant response headers to URL-encoded variants of static file paths, allowing attackers to bypass header-based security controls by requesting percent-encoded forms of protected resources. This affects Rack versions prior to 2.2.23, 3.1.21, and 3.2.6, and is particularly dangerous in deployments relying on Rack::Static to enforce Content-Security-Policy, X-Frame-Options, or similar protective headers on static content. No public exploit code or active exploitation has been confirmed at time of analysis.

Rack's multipart form data parser uses a greedy regular expression that selects the last boundary parameter from a Content-Type header instead of the first, allowing request smuggling when upstream proxies or WAFs interpret the first boundary. This mismatch enables attackers to bypass upstream inspection by crafting multipart requests with duplicate boundary declarations, causing Rack to parse a different body structure than the intermediary validated. Affected versions are Rack prior to 2.2.23, 3.1.21, and 3.2.6; patches are available for all three release branches.

Rack web server interface versions prior to 2.2.23, 3.1.21, and 3.2.6 fail to properly escape regex metacharacters when constructing directory path filtering expressions, causing the Rack::Directory component to expose full filesystem paths in HTML directory listings. An unauthenticated remote attacker can retrieve sensitive path information by requesting directory listings when the configured root path contains regex special characters such as +, *, or ., achieving low-confidentiality impact with CVSS 5.3. No public exploit code or active exploitation has been confirmed at time of analysis.