Vulnerability · Published May 11, 2026 · Assigned by GitHub_M
CVE-2026-42874Microdot: HTTP response splitting in Response.set_cookie()
Low 3.7
In plain English
A low-severity security flaw in microdot from miguelgrinberg. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 12% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| PyPI | microdot | 2.6.1 | GHSA-7wc8-wvc4-m498 |
| PyPI | microdot | 2.6.1 | PYSEC-2026-2646 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| miguelgrinberg | microdot | < 2.6.1 |
Weakness: CWE-113 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N