Is CVE-2026-26961 actively exploited?

CVE-2026-26961 has no public evidence of in-the-wild exploitation as of 2026-04-16.

What is the CVSS score for CVE-2026-26961?

CVE-2026-26961 has a CVSS score of 3.7 (LOW severity). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N.

How do I patch CVE-2026-26961?

Patch guidance is available from rack security advisories. CVEDatabase generates AI-assisted remediation guidance on demand for CVE-2026-26961.

Which products are affected by CVE-2026-26961?

3 products: rack rack, rack rack, rack rack.

CVE-2026-26961 - remediation guidance & executive summary

Description

Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Multipart::Parser extracts the boundary parameter from multipart/form-data using a greedy regular expression. When a Content-Type header contains multiple boundary parameters, Rack selects the last one rather than the first. In deployments where an upstream proxy, WAF, or intermediary interprets the first boundary parameter, this mismatch can allow an attacker to smuggle multipart content past upstream inspection and have Rack parse a different body structure than the intermediary validated. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.

CVSS Metrics

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Attack Vector: network
Complexity: high
Privileges: none
User Action: none
Scope: unchanged
Confidentiality: none
Integrity: low
Availability: none
Weaknesses: CWE-436

Metadata

Primary Vendor: RACK
Published: 4/2/2026
Last Modified: 4/16/2026
Source: NIST NVD
Note: Verify all details with official vendor sources before applying patches.

Affected Products

rack : rackrack : rackrack : rack

Remediation Guidance

Executive Summary

Cite this page

CVE-2026-26961. CVEDatabase.com. Retrieved 1 May 2026. https://cvedatabase.com/cve/CVE-2026-26961

View on NIST NVD

CVE-2026-26961 vulnerability