CVE-2026-42874 json
Microdot: HTTP response splitting in Response.set_cookie()
published 6mo ago modified 14d ago also GHSA-7wc8-wvc4-m498 , PYSEC-2026-2646 , EUVD-2026-29189
- cvss
- 3.7
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 12%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
Is CVE-2026-42874 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 5mo ago
Exploit prediction
0.22% chance of exploitation in the next 30 days, higher than 12% of all scored CVEs (FIRST EPSS, 2026-11-09).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 3.7 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N |
| OSV | 3.1 | 3.7 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N |
| GitHub | 3.1 | 3.7 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | microdot | <2.6.1 |
2.6.1 |
Affected products
- miguelgrinberg microdot
Classification
- Weakness
-
- CWE-113 Improper Neutralization of CRLF Sequences in HTTP Headers
References
-
github.com
/miguelgrinberg/microdot/commit/99b281b45faef8472410f2d56bfef496dfbd95d5
web
-
github.com
/miguelgrinberg/microdot/security/advisories/GHSA-7wc8-wvc4-m498
web
-
github.com
/miguelgrinberg/microdot/blob/main/CHANGES.md
web
-
nvd.nist.gov
/vuln/detail/CVE-2026-42874
advisory
-
github.com
/miguelgrinberg/microdot
package
-
pypi.org
/project/microdot
package
-
github.com
/advisories/GHSA-7wc8-wvc4-m498
advisory
Sources
- CVE List CVE-2026-42874
- GitHub Advisory GHSA-7wc8-wvc4-m498
- NVD CVE-2026-42874
- OSV PYSEC-2026-2646
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