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CVE-2026-34230

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CVE-2026-34230

Published: Apr 2, 2026

Modified: Apr 3, 2026

PUBLISHED

CVSS v3.1

5.3

MEDIUM

Description

Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Utils.select_best_encoding processes Accept-Encoding values with quadratic time complexity when the header contains many wildcard (*) entries. Because this method is used by Rack::Deflater to choose a response encoding, an unauthenticated attacker can send a single request with a crafted Accept-Encoding header and cause disproportionate CPU consumption on the compression middleware path. This results in a denial of service condition for applications using Rack::Deflater. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.

VendorProductVersions

rack

rack

affected
< 2.2.23
affected
>= 3.0.0.beta1, < 3.1.21
affected
>= 3.2.0, < 3.2.6

Weaknesses (CWE)

CWE-400
CWE-407

CVSS v3.1 Details

CVSS v3.1 Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

Low

References

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