chore(deps): update dependency form-data to v4.0.6 [security]

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
form-data	4.0.4 → 4.0.6

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form-data uses unsafe random function in form-data for choosing boundary

CVE-2025-7783 / GHSA-fjxv-7rqg-78g4

More information

Details

Summary

form-data uses Math.random() to select a boundary value for multipart form-encoded data. This can lead to a security issue if an attacker:

1. can observe other values produced by Math.random in the target application, and
2. can control one field of a request made using form-data

Because the values of Math.random() are pseudo-random and predictable (see: https://blog.securityevaluators.com/hacking-the-javascript-lottery-80cc437e3b7f), an attacker who can observe a few sequential values can determine the state of the PRNG and predict future values, includes those used to generate form-data's boundary value. The allows the attacker to craft a value that contains a boundary value, allowing them to inject additional parameters into the request.

This is largely the same vulnerability as was recently found in undici by parrot409 -- I'm not affiliated with that researcher but want to give credit where credit is due! My PoC is largely based on their work.

Details

The culprit is this line here: https://github.com/form-data/form-data/blob/426ba9ac440f95d1998dac9a5cd8d738043b048f/lib/form_data.js#L347

An attacker who is able to predict the output of Math.random() can predict this boundary value, and craft a payload that contains the boundary value, followed by another, fully attacker-controlled field. This is roughly equivalent to any sort of improper escaping vulnerability, with the caveat that the attacker must find a way to observe other Math.random() values generated by the application to solve for the state of the PRNG. However, Math.random() is used in all sorts of places that might be visible to an attacker (including by form-data itself, if the attacker can arrange for the vulnerable application to make a request to an attacker-controlled server using form-data, such as a user-controlled webhook -- the attacker could observe the boundary values from those requests to observe the Math.random() outputs). A common example would be a x-request-id header added by the server. These sorts of headers are often used for distributed tracing, to correlate errors across the frontend and backend. Math.random() is a fine place to get these sorts of IDs (in fact, opentelemetry uses Math.random for this purpose)

PoC

PoC here: https://github.com/benweissmann/CVE-2025-7783-poc

Instructions are in that repo. It's based on the PoC from https://hackerone.com/reports/2913312 but simplified somewhat; the vulnerable application has a more direct side-channel from which to observe Math.random() values (a separate endpoint that happens to include a randomly-generated request ID).

Impact

For an application to be vulnerable, it must:

• Use form-data to send data including user-controlled data to some other system. The attacker must be able to do something malicious by adding extra parameters (that were not intended to be user-controlled) to this request. Depending on the target system's handling of repeated parameters, the attacker might be able to overwrite values in addition to appending values (some multipart form handlers deal with repeats by overwriting values instead of representing them as an array)
• Reveal values of Math.random(). It's easiest if the attacker can observe multiple sequential values, but more complex math could recover the PRNG state to some degree of confidence with non-sequential values.

If an application is vulnerable, this allows an attacker to make arbitrary requests to internal systems.

Severity

• CVSS Score: 9.4 / 10 (Critical)
• Vector String: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N

References

• https://github.com/form-data/form-data/security/advisories/GHSA-fjxv-7rqg-78g4
• https://nvd.nist.gov/vuln/detail/CVE-2025-7783
• https://github.com/form-data/form-data/commit/3d1723080e6577a66f17f163ecd345a21d8d0fd0
• https://github.com/benweissmann/CVE-2025-7783-poc
• https://lists.debian.org/debian-lts-announce/2025/07/msg00023.html
• https://github.com/advisories/GHSA-fjxv-7rqg-78g4

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

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form-data: CRLF injection in form-data via unescaped multipart field names and filenames

CVE-2026-12143 / GHSA-hmw2-7cc7-3qxx

More information

Details

Summary

form-data builds multipart/form-data request bodies. Through v4.0.5, the field name passed to FormData#append and the filename option are concatenated directly into the Content-Disposition header with no escaping of CR (\r), LF (\n), or ". An application that uses untrusted input as a field name or filename therefore lets an attacker terminate the header line and either inject additional headers or smuggle whole additional multipart parts into the request the application forwards to a backend.

This is CWE-93 (CRLF injection). It is a divergence from how browsers and the WHATWG HTML spec serialize form-data (they escape these characters), so the fix is to match that behavior. Severity is conditional: it depends on the consuming application passing attacker-controlled data as a field name or filename. Applications that only use fixed/trusted field names are not affected.

Details

In lib/form_data.js, _multiPartHeader builds the part header as:

'Content-Disposition': ['form-data', 'name="' + field + '"'].concat(contentDisposition || [])

and _getContentDisposition builds filename="' + filename + '"'. Neither escapes control characters, so a \r\n in field/filename ends the header line. The same applies to ", which can break out of the quoted parameter.

Proof of concept

const FormData = require('form-data');
const form = new FormData();
form.append('email"\r\nX-Injected: true\r\nfake="', 'user@example.com');
console.log(form.getBuffer().toString());

Before the fix this emits an injected X-Injected: true header line. A field name that also includes --<boundary> sequences can introduce additional parts (e.g. an extra name="is_admin" field), which a downstream parser accepts as legitimate.

Impact

For an application that uses untrusted field names/filenames:

• Field injection / override (integrity). Inject or override fields the backend trusts (e.g. is_admin, role) — the primary demonstrated impact.
• Header injection into the generated multipart part.

Claims of guaranteed privilege escalation, authentication bypass, high confidentiality impact, and availability impact are application-dependent downstream consequences, not properties of form-data itself, and are not demonstrated by the PoC.

Severity

The demonstrated, library-attributable impact is integrity (field/header injection); there is no demonstrated confidentiality disclosure or availability impact in form-data itself, and exploitation requires the consuming app to feed untrusted data into field names/filenames. A Moderate (≈5.3, I:L) rating is also defensible given that precondition.

Patch

Fixed in 4.0.6, 3.0.5, and 2.5.6. Users on older 0.x/1.x/2.x releases should upgrade to 2.5.6 or later.

The fix escapes \r, \n, and " as %0D, %0A, and %22 in field names and filenames, matching the WHATWG HTML multipart/form-data encoding algorithm that browsers implement. This neutralizes the injection while leaving ordinary field names (including name[0], dotted, and unicode names) unchanged.

Workaround

Until upgrading, validate or reject field names/filenames that contain control characters before calling append:

if (/[\r\n]/.test(field)) { throw new Error('invalid field name'); }

Credit

Reported by yueyueL.

Severity

• CVSS Score: 8.7 / 10 (High)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

References

• https://github.com/form-data/form-data/security/advisories/GHSA-hmw2-7cc7-3qxx
• https://nvd.nist.gov/vuln/detail/CVE-2026-12143
• https://github.com/form-data/form-data/commit/64190db548c0179e37206858e39f27cf513e9435
• https://github.com/form-data/form-data/commit/be3f3cf553978bac15a5182f1f3c3d2d38ccf229
• https://github.com/form-data/form-data/commit/c7133499c2ee1b80c678e411244f4442bf902045
• https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#multipart-form-data
• https://www.npmjs.com/package/form-data
• https://github.com/advisories/GHSA-hmw2-7cc7-3qxx

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

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Release Notes

form-data/form-data (form-data)

v4.0.6

Compare Source

Commits

• [Fix] escape CR, LF, and " in field names and filenames 8dff42c
• [Dev Deps] update @ljharb/eslint-config, auto-changelog, tape f31d21e
• [Deps] update hasown, mime-types 92ae0eb
• [Dev Deps] update js-randomness-predictor 67b0f65

v4.0.5

Compare Source

Commits

• [Tests] Switch to newer v8 prediction library; enable node 24 testing 16e0076
• [Dev Deps] update @ljharb/eslint-config, eslint 5822467
• [Fix] set Symbol.toStringTag in the proper place 76d0dee

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