HTTPX2: Multipart part header injection via unvalidated file Content-Type and custom headers

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-84379: 0.32% estimated exploitation activity in the next 30 days; percentile 24.72 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary HTTPX2 serializes the per-file Content-Type and custom headers supplied through the files= tuple API directly into the multipart/form-data body without validating custom header names or values. An attacker who can influence upload metadata passed to HTTPX2 can use CR or LF characters to terminate a multipart part header and inject additional part headers or end the part header block early. Details The three-element file tuple accepts (filename, content, contenttype), and the four-element form accepts (filename, content, contenttype, headers). FileField.renderheaders() interpolates the supplied header names and values between CRLF delimiters without validating them. For example: The generated body contains an attacker-injected part header: The same issue affects names and values in the custom header mapping from the four-element tuple. Field names and filenames are serialized through a separate escaping path and do not permit CRLF header injection. Impact Applications are…

Published by the source

8 Sep 2026, 20:45 UTC

Last modified by the source

10 Sep 2026, 12:25 UTC

Source last checked

26 Oct 2026, 13:51 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-h4x7-gw46-3wm6

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-h4x7-gw46-3wm6

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-h4x7-gw46-3wm6

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# Patch Next advisory brief: CVE-2026-84379

Advisory: HTTPX2: Multipart part header injection via unvalidated file Content-Type and custom headers
IDs: CVE-2026-84379, GHSA-h4x7-gw46-3wm6
Record: https://patchnext.com/advisories/cve-2026-84379 (revision 3, source checked 26 Oct 2026, 13:51 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: httpx2 2.11.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI httpx2: affected < 2.11.0; fixed in 2.11.0

## Suggested inspection (read-only)
- `python -m pip show httpx2`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on httpx2.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-h4x7-gw46-3wm6 (GitHub-reviewed advisory GHSA-h4x7-gw46-3wm6 lists affected ranges: PyPI httpx2 >=0 <2.11.0)
- Verified: https://osv.dev/vulnerability/GHSA-h4x7-gw46-3wm6 (OSV record GHSA-h4x7-gw46-3wm6 lists affected ranges: PyPI httpx2 >=0 <2.11.0 (fixed))

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