What’s Vulnerable › Vulnerabilities
CVE-2026-34826: Rack: Unbounded Range Count in get_byte_ranges Enables DoS
- Severity: high (CVSS 7.5 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.4% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-04-02 · updated 2026-07-24
- Weakness: CWE-400
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.
Affected products
- rack: before 2.2.23; from 3.0.0 before 3.1.21; from 3.2.0 before 3.2.6 — fixed in 2.2.23, 3.1.21, 3.2.6
- Rubygems Rack: before 2.2.23; from 3.0.0.beta1 before 3.1.21; from 3.2.0 before 3.2.6; 0.1.0, 0.2.0, 0.3.0, 0.4.0, 0.9.0, 0.9.1 (+169) — fixed in 2.2.23, 3.1.21, 3.2.6
How to fix
Upgrade to a fixed version: rack 2.2.23, 3.1.21, 3.2.6; Rubygems Rack 2.2.23, 3.1.21, 3.2.6. Check the vendor advisory for mitigations.
References
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