# CVE-2026-12143: form-data does not escape CR/LF/quote in multipart field names and filenames (CRLF injection)

CVE-2026-12143 is fixed in 7 products on 1 platform, first by DEBIAN-CVE-2026-12143, released June 27, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-12143
- Priority: High
- CVSS: 7.5 (Important)
- EPSS: 0.0067
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 12, 2026
- Weakness: Improper Neutralization of CRLF Sequences ('CRLF Injection')
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-12143

## Description

form-data is a library for creating readable multipart/form-data streams. In versions through 4.0.5, the `field` argument to `FormData#append` and the `filename` option are concatenated verbatim into the `Content-Disposition` header without escaping carriage return (CR), line feed (LF), or double-quote (") characters. An application that passes attacker-controlled data as a field name or filename (for example, an API gateway that turns JSON object keys into multipart field names) allows the attacker to terminate the header line and inject additional headers, or to smuggle entire additional multipart parts, into the request the application forwards to a backend. This can let the attacker add or override form fields (e.g. set `is_admin=true`) seen by the downstream parser. This is an instance of CWE-93 (CRLF injection). The fix escapes CR, LF, and `"` as `%0D`, `%0A`, and `%22` in field names and filenames, matching the serialization browsers use per the WHATWG HTML multipart/form-data encoding algorithm. Exploitation requires the consuming application to use untrusted input as a field name or filename; applications that use only fixed/trusted field names are not affected. Fixed in 2.5.6, 3.0.5, and 4.0.6.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | agama-web-ui opensuse-leap 16.0 | 17+673.b97ba64d6-160000.12.1 | [OPENSUSE-SU-2026:21448-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21448-1.md) | Jul 27, 2026 |
| Linux | node-form-data Debian 14 | 4.0.6+~2.1.0-1 | [DEBIAN-CVE-2026-12143](https://patchblox.com/security/data/fix/linux/debian-cve-2026-12143.md) | Jun 27, 2026 |
| Linux | python-jupytext Fedora 43 | 1.19.6-1.fc43 | [FEDORA-2026-3942AB86FD](https://patchblox.com/security/data/fix/linux/fedora-2026-3942ab86fd.md) | Oct 5, 2026 |
| Linux | python-jupytext-doc Fedora 43 | 1.19.6-1.fc43 | [FEDORA-2026-3942AB86FD](https://patchblox.com/security/data/fix/linux/fedora-2026-3942ab86fd.md) | Oct 5, 2026 |
| Linux | python3-jupyterlab-jupytext Fedora 43 | 1.19.6-1.fc43 | [FEDORA-2026-3942AB86FD](https://patchblox.com/security/data/fix/linux/fedora-2026-3942ab86fd.md) | Oct 5, 2026 |
| Linux | python3-jupytext Fedora 43 | 1.19.6-1.fc43 | [FEDORA-2026-3942AB86FD](https://patchblox.com/security/data/fix/linux/fedora-2026-3942ab86fd.md) | Oct 5, 2026 |
| Linux | rh-podman-desktop RHEL 10 | 1.1.2-1.el10_2 | [RHSA-2026:57590](https://patchblox.com/security/data/fix/linux/rhsa-2026-57590.md) | Aug 21, 2026 |

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Data as of 2026-11-09T07:25:28Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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