CVE-2026-42874 LOW

CVE-2026-42874: Microdot: HTTP response splitting in Response.set_cookie()

Vendor Miguelgrinberg
Product microdot
Weakness CWE-113 · HTTP response splitting
Published May 11, 2026
Last update May 13, 2026

CVSS base score

3.7/10
Attack vector Network
Attack complexity High
Privileges required None
User interaction None
Confidentiality None
Integrity Low

CVSS vector

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

What the vulnerability does

01Description

Microdot is a minimalistic Python web framework. Prior to 2.6.1, the Response.set_cookie() method does not sanitize its string arguments, and in particular will not detect the presence of the \r\n sequence in them. This can be a potential source of header injection attacks. For a header injection attack through this issue to be possible, an attacker must first infiltrate the client (for example through an independent XSS attack), so that it can send malicious information that is destined to be stored in a cookie by the server on behalf of the victim. An attacker that infiltrates one client can only orchestrate a header injection attack for that client, all other clients that were not infiltrated are safe. This vulnerability is fixed in 2.6.1.

Key dates

02Disclosure timeline

May 11, 2026 CVE published
May 13, 2026 Record updated