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Pin vulnerable form-data transitive dependencies - #706

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copilot/fix-form-data-unsafe-random-function
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abstractj with Copilot wants to merge 2 commits into
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copilot/fix-form-data-unsafe-random-function

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Copilot AI commented Jun 3, 2026 •

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This updates the vulnerable form-data resolution for GHSA-fjxv-7rqg-78g4 / CVE-2025-7783 to patched versions. The vulnerable boundary-generation path is not used by runtime adapter code in this repository, but it is present in development/test dependency resolution and should not remain in the lockfile.

  • What changed

    • Added scoped npm overrides to pin legacy request consumers to form-data@2.5.4
    • Added scoped npm overrides to pin axios consumers to form-data@4.0.4
    • Refreshed package-lock.json through npm so vulnerable resolutions are removed without changing application code
  • Reachability Assessment

    • Advisory scope: multipart form construction in form-data, specifically boundary selection
    • Repository search found direct usage only in test support (test/utils/token.mjs via keycloak-request-token)
    • Runtime adapter modules do not import form-data, request, or keycloak-request-token
    • Assessment: not reachable from shipped runtime code; limited to dev/test dependency paths
    • Confidence: high
  • Dependency resolution

    "overrides": {
      "request": {
        "form-data": "2.5.4"
      },
      "axios": {
        "form-data": "4.0.4"
      }
    }
Original prompt

This section details the Dependabot vulnerability alert you should resolve

<alert_title>form-data uses unsafe random function in form-data for choosing boundary</alert_title>
<alert_description>### 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.</alert_description>

critical
GHSA-fjxv-7rqg-78g4, CVE-2025-7783
form-data
npm
<vulnerable_versions>2.3.3</vulnerable_versions>
<patched_version>2.5.4</patched_version>
<manifest_path>package-lock.json</manifest_path>

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

<task_instructions>Resolve this alert by updating the affected package to a non-vulnerable version. Prefer the lowest non-vulnerable version (see the patched_version field above) over the latest to minimize breaking changes. Include a Reachabil...

Copilot AI changed the title [WIP] Fix vulnerability in form-data using unsafe random function Pin vulnerable form-data transitive dependencies Jun 3, 2026
Copilot AI requested a review from abstractj June 3, 2026 16:13
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