High 7.5Published Apr 2, 2026

CVE-2026-34827Rack is a modular Ruby web server interface.

Updated under an hour ago (2026-10-19 07:00 UTC)

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Every CVE for rack

Exploited in the last 30 days

Rack is a modular Ruby web server interface. From versions 3.0.0.beta1 to before 3.1.21, and 3.2.0 to before 3.2.6, Rack::Multipart::Parser#handle_mime_head parses quoted multipart parameters such as Content-Disposition: form-data; name="..." using repeated String#index searches combined with String#slice! prefix deletion. For escape-heavy quoted values, this causes super-linear processing. An unauthenticated attacker can send a crafted multipart/form-data request containing many parts with long backslash-escaped parameter values to trigger excessive CPU usage during multipart parsing. This results in a denial of service condition in Rack applications that accept multipart form data. This issue has been patched in versions 3.1.21 and 3.2.6.

CVSS: 7.5 HIGH (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-400, CWE-407, CWE-770
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Not given
NVD analysis: Modified
Record last updated: Jul 24, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

rack rack rack:rack	from 3.0.0 before 3.1.21; from 3.2.0 before 3.2.6	NVD

References

https://github.com/rack/rack/security/advisories/GHSA-v6x5-cg8r-vv6xmitigation, vendor-advisory
https://access.redhat.com/security/cve/CVE-2026-34827
https://bugzilla.redhat.com/show_bug.cgi?id=2454501
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34827.json

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.