CVE-2026-42561
Prior to 0.0.27, python-multipart has a denial of service vulnerability in multipart part header parsing.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.74%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.27, python-multipart has a denial of service vulnerability in multipart part header parsing. When parsing multipart/form-data, MultipartParser previously had no limit on the number of part headers or the size of an individual part header. An attacker could send a request with either many repeated headers without terminating the header block or a single very large header value, causing excessive CPU work before request rejection or completion. This vulnerability is fixed in 0.0.27.
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 0.74% probability · 53th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-770, CWE-606
- Source
- security-advisories@github.com
References
- https://github.com/Kludex/python-multipart/security/advisories/GHSA-pp6c-gr5w-3c5g
- https://access.redhat.com/errata/RHSA-2026:37275
- https://access.redhat.com/errata/RHSA-2026:42132
- https://access.redhat.com/errata/RHSA-2026:42142
- https://access.redhat.com/errata/RHSA-2026:43038
- https://access.redhat.com/errata/RHSA-2026:44696
- https://access.redhat.com/errata/RHSA-2026:51194
- https://access.redhat.com/errata/RHSA-2026:51219
- https://access.redhat.com/errata/RHSA-2026:51357
- https://access.redhat.com/security/cve/CVE-2026-42561
- https://bugzilla.redhat.com/show_bug.cgi?id=2477309
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42561.json
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.