CVE-2025-22150

Undici is an HTTP/1.1 client. Starting in version 4.5.0 and prior to versions 5.28.5, 6.21.1, and 7.2.3, undici uses Math.random() to choose the boundary for a multipart/form-data request. It is known that the output of Math.random() can be predicted if several of its generated values are known. If there is a mechanism in an app that sends multipart requests to an attacker-controlled website, they can use this to leak the necessary values. Therefore, an attacker can tamper with the requests going to the backend APIs if certain conditions are met. This is fixed in versions 5.28.5, 6.21.1, and 7.2.3. As a workaround, do not issue multipart requests to attacker controlled servers.

Weakness

The product uses insufficiently random numbers or values in a security context that depends on unpredictable numbers.

Affected Software

Potential Mitigations

• Use a well-vetted algorithm that is currently considered to be strong by experts in the field, and select well-tested implementations with adequate length seeds.
• In general, if a pseudo-random number generator is not advertised as being cryptographically secure, then it is probably a statistical PRNG and should not be used in security-sensitive contexts.
• Pseudo-random number generators can produce predictable numbers if the generator is known and the seed can be guessed. A 256-bit seed is a good starting point for producing a “random enough” number.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/112.html
• https://cwe.mitre.org/data/definitions/485.html
• https://cwe.mitre.org/data/definitions/59.html

References

• https://blog.securityevaluators.com/hacking-the-javascript-lottery-80cc437e3b7f
• https://github.com/nodejs/undici/blob/8b06b8250907d92fead664b3368f1d2aa27c1f35/lib/web/fetch/body.js#L113
• https://github.com/nodejs/undici/commit/711e20772764c29f6622ddc937c63b6eefdf07d0
• https://github.com/nodejs/undici/commit/c2d78cd19fe4f4c621424491e26ce299e65e934a
• https://github.com/nodejs/undici/commit/c3acc6050b781b827d80c86cbbab34f14458d385
• https://github.com/nodejs/undici/security/advisories/GHSA-c76h-2ccp-4975
• https://hackerone.com/reports/2913312