What Is CVE‑2025‑7783?
On July 18, 2025, a critical vulnerability was disclosed in form-data, a widely used JavaScript library for creating multipart/form-data requests. The flaw arises because the library generates multipart boundaries using JavaScript’s Math.random() function, which is not cryptographically secure. As a result, the boundaries can be predicted, allowing attackers to manipulate how backend systems interpret form submissions.
This vulnerability affects all releases prior to 2.5.4, as well as 3.0.0–3.0.3 and 4.0.0–4.0.3. It carries a CVSS v4 score of 9.4 (Critical) due to its high potential impact on confidentiality, integrity, and - in some cases - availability. You can read more in CybersecurityNews’ detailed coverage.
How the Vulnerability Is Exploited
At its core, the exploit relies on the predictability of Math.random(). If an attacker can observe several outputs from this function - for example, via request IDs, trace headers, or other fields generated during the same process - they can reverse‑engineer the internal state of the pseudo‑random number generator. Once they know the state, they can forecast future outputs with high accuracy.
form-data uses Math.random() to generate multipart boundaries. An attacker who can predict those boundaries can craft malicious multipart payloads with exactly the same markers, injecting additional fields or replacing existing ones in a way that the backend will interpret as legitimate user input.
This makes HTTP parameter pollution possible - for example, overwriting critical form fields such as role=admin, injecting malicious file uploads, or bypassing validation rules. Depending on how the application processes the request, this could lead to privilege escalation, unauthorized data access, or even remote code execution.
The Real-World Impact
The biggest reason CVE‑2025‑7783 is dangerous is its reach. form-data is a dependency in millions of npm downloads per week and is used in APIs, file upload services, webhook handlers, and internal automation scripts. Many developers don’t install it directly - it often comes bundled inside other popular packages such as request libraries, SDKs for cloud services, or testing frameworks.
In practice, this means that even teams who have never consciously chosen form-data may be vulnerable. A small dependency update in an upstream package could silently pull in an affected version. That’s why detecting and fixing the issue manually is so hard: you need to scan deep into transitive dependencies across all projects, repositories, and environments.
This kind of flaw also has an unusually low exploitation barrier in certain environments. In microservice architectures, for example, internal services often share trace IDs or debugging headers that include Math.random() values - making it easier for an attacker who has access to one service to attack another. In public‑facing APIs, especially those that handle file uploads, the risk can extend to arbitrary code injection in processing pipelines.
How Resolved Creates and Deploys the Patch
When CVE‑2025‑7783 was disclosed, Resolved Security patching machine moved quickly - releasing a working fix in under 24 hours. The speed comes from an automated vulnerability intelligence pipeline that monitors CVE feeds, GitHub security advisories, and vendor patches in real time.
Here’s how the patching process works behind the scenes:
Once a CVE is published, Resolved’s scanners sweep all monitored codebases - including deeply nested dependencies - to identify every vulnerable instance. The system then pulls the vendor’s fixed version (2.5.4, 3.0.4, or 4.0.4) and, if needed, applies a custom patch replacing the Math.random() boundary generation with a secure crypto.randomBytes() implementation.
All patched packages pass full quality assurance through regression tests, ensuring functional equivalence with the original - they are drop‑in replacements that require no changes to your own code.
With one click, the upgrade is deployed across all affected environments, committing changes to repositories or updating package locks automatically. A final scan confirms that every vulnerable version has been replaced and no outdated copies remain.
This approach eliminates the weeks or months it often takes for organizations to discover, triage, and manually patch vulnerabilities like this.
Moving Forward
For organizations without automated remediation, addressing CVE‑2025‑7783 means manually finding and upgrading vulnerable versions, ensuring no transitive dependencies reintroduce them, and checking that no Math.random()-based outputs are exposed. This process is time‑consuming and error‑prone - and every day spent waiting increases the risk of exploitation.
With Resolved’s automated approach, the gap between vulnerability disclosure and complete protection can be reduced to hours, not weeks.
Protect Your Stack Now
CVE‑2025‑7783 is a perfect example of a small coding choice - using a weak random number generator - having a massive security impact when embedded deep in the supply chain. The exploit path is simple, the exposure is wide, and the consequences can be severe.
Book a demo with Resolved Security to see how you can detect, patch, and verify fixes for vulnerabilities like this across your entire software stack - all in a matter of minutes.
See How to Patch CVE‑2025‑7783 in Minutes.
