CVE-2026-34826— Rack: Unbounded Range Count in get_byte_ranges Enables DoS
Quick assessment
Affected
rack rack
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
Rack是Rack开源的一个模块化的Ruby web服务器界面。 Rack 2.2.23之前版本、3.1.21之前版本和3.2.6之前版本存在安全漏洞，该漏洞源于Rack::Utils.get_byte_ranges解析HTTP Range标头时未限制单个字节范围的数量，可能导致拒绝服务。
Possible ATT&CK Techniques 1 AI
T1499 · Endpoint Denial of Service
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I. Basic Information for CVE-2026-34826
Vulnerability Information
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Vulnerability Title
Rack: Unbounded Range Count in get_byte_ranges Enables DoS
Source: CVE Program / CVE List V5
Vulnerability Description
Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Utils.get_byte_ranges parses the HTTP Range header without limiting the number of individual byte ranges. Although the existing fix for CVE-2024-26141 rejects ranges whose total byte coverage exceeds the file size, it does not restrict the count of ranges. An attacker can supply many small overlapping ranges such as 0-0,0-0,0-0,... to trigger disproportionate CPU, memory, I/O, and bandwidth consumption per request. This results in a denial of service condition in Rack file-serving paths that process multipart byte range responses. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5
Vulnerability Title
Rack 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Rack是Rack开源的一个模块化的Ruby web服务器界面。 Rack 2.2.23之前版本、3.1.21之前版本和3.2.6之前版本存在安全漏洞，该漏洞源于Rack::Utils.get_byte_ranges解析HTTP Range标头时未限制单个字节范围的数量，可能导致拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
II. Public POCs for CVE-2026-34826
| # | POC Description | Source Link | Shenlong Link |
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Vendor Advisories for CVE-2026-34826 (1)
Same Patch Batch · rack · 2026-04-02 · 13 CVEs total
| CVE-2026-34785 | 7.5 HIGH | Rack: Local file inclusion in `Rack::Static` via URL Prefix Matching |
| CVE-2026-34827 | 7.5 HIGH | Rack: Algorithmic-Complexity DoS in Rack::Multipart::Parser |
| CVE-2026-34829 | 7.5 HIGH | Rack: Denial of Service via Unbounded Multipart File Upload Without Content-Length |
| CVE-2026-34830 | 5.9 MEDIUM | Rack: Rack::Sendfile regex injection via HTTP_X_ACCEL_MAPPING header allows arbitrary file |
| CVE-2026-34786 | 5.3 MEDIUM | Rack: Rack::Static header_rules bypass via URL-encoded paths |
| CVE-2026-34763 | 5.3 MEDIUM | Rack: Rack::Directory info disclosure and DoS via unescaped regex interpolation |
| CVE-2026-34230 | 5.3 MEDIUM | Rack: Quadratic complexity in Rack::Utils.select_best_encoding via wildcard Accept-Encodin |
| CVE-2026-26962 | 4.8 MEDIUM | Rack: Header injection in multipart requests |
| CVE-2026-32762 | 4.8 MEDIUM | Rack: Forwarded Header semicolon injection enables Host and Scheme spoofing |
| CVE-2026-34835 | 4.8 MEDIUM | Rack: `Rack::Request` accepts invalid Host characters, enabling host allowlist bypass. |
| CVE-2026-34831 | 4.8 MEDIUM | Rack: Content-Length mismatch in Rack::Files error responses |
| CVE-2026-26961 | 3.7 LOW | Rack: Multipart Boundary Parsing Ambiguity allowing WAF Bypass |
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