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Vulnerability · Published Jun 12, 2026 · Assigned by harborist

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

High 7.5

In plain English

A high-severity security flaw in form-data from form-data. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 52% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High
Exploit odds (30 days)0.7%top 47.9% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12node-form-datano fix listedDEBIAN-CVE-2026-12143
Debian:13node-form-datano fix listedDEBIAN-CVE-2026-12143
Debian:14node-form-data4.0.6+~2.1.0-1DEBIAN-CVE-2026-12143
Ubuntu:24.04:LTSnode-form-datano fix listedUBUNTU-CVE-2026-12143
Ubuntu:25.10node-form-datano fix listedUBUNTU-CVE-2026-12143
Ubuntu:26.04:LTSnode-form-datano fix listedUBUNTU-CVE-2026-12143
Ubuntu:26.10node-form-datano fix listedUBUNTU-CVE-2026-12143
npmform-data4.0.6GHSA-hmw2-7cc7-3qxx
npmform-data3.0.5GHSA-hmw2-7cc7-3qxx
npmform-data2.5.6GHSA-hmw2-7cc7-3qxx

Affected products (as reported)

VendorProductVersions
form-data form-data 0 – before 2.5.63.0.0 – before 3.0.54.0.0 – before 4.0.6

Weakness: CWE-93 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

References