UBUNTU-CVE-2026-34826: High severity ubuntu/ruby-rack vulnerability
Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Utils.getbyteranges 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 Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
ubuntu/ruby-rackto a version that resolves this vulnerability.Fixed in 1.6.4-3ubuntu0.2+esm10 - Upgrade
Upgrade
ubuntu/ruby-rackto a version that resolves this vulnerability.Fixed in 1.6.4-4ubuntu0.2+esm10 - Upgrade
Upgrade
ubuntu/ruby-rackto a version that resolves this vulnerability.Fixed in 2.1.4-5ubuntu1.2+esm3 - Upgrade
Upgrade
ubuntu/ruby-rackto a version that resolves this vulnerability.Fixed in 2.2.7-1ubuntu0.7 - Upgrade
Upgrade
ubuntu/ruby-rackto a version that resolves this vulnerability.Fixed in 3.1.16-0.1ubuntu0.3 - Upgrade
Upgrade
Rackto a version that resolves this vulnerability.Fixed in 2.2.23 - Upgrade
Upgrade
Rackto a version that resolves this vulnerability.Fixed in 3.1.21 - Upgrade
Upgrade
Rackto a version that resolves this vulnerability.Fixed in 3.2.6
Event History
Frequently Asked Questions
Which deployments are exposed to this denial-of-service issue?
Ubuntu systems using ruby-rack versions earlier than 2.2.23, 3.1.21, or 3.2.6 are affected when Rack file-serving paths process multipart HTTP byte-range responses.
What does an attacker need to exploit it?
An unauthenticated remote attacker can send an HTTP Range header containing many small overlapping ranges. No user interaction or privileges are required.
What is the operational impact of a malicious request?
Processing a request with many overlapping ranges can cause disproportionate CPU, memory, I/O, and bandwidth consumption, resulting in denial of service.
How can this issue be remediated?
Update Rack to version 2.2.23, 3.1.21, or 3.2.6, as applicable to the deployed release line.