CVE-2026-34230 describes a denial of service vulnerability in Rack, a Ruby web server interface, affecting versions prior to 2.2.23, 3.1.21, and 3.2.6. The flaw arises from quadratic time complexity when Rack::Utils.select_best_encoding processes Accept-Encoding headers containing multiple wildcard entries, particularly impacting applications using Rack::Deflater. An unauthenticated attacker can exploit this with a single, crafted request to cause disproportionate CPU consumption, leading to a denial of service condition. Rated Medium severity (CVSS 5.3), there is currently no evidence of active exploitation, public exploit code, or significant community attention.
| Vendor | Product | Version(s) | CPE |
|---|---|---|---|
< 2.2.23CPE matchmatch criteria | cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:* | ||
>= 3.0.0, < 3.1.21CPE matchmatch criteria | cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:* | ||
>= 3.2.0, < 3.2.6CPE matchmatch criteria | cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:* |
CVSS version used by this source: 3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.
The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.