CVE-2022-39218: Random number seed fixed during compilation

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.9% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2022-09-20 · updated 2026-06-17
Weakness: CWE-335

Description

The JS Compute Runtime for Fastly's Compute@Edge platform provides the environment JavaScript is executed in when using the Compute@Edge JavaScript SDK. In versions prior to 0.5.3, the `Math.random` and `crypto.getRandomValues` methods fail to use sufficiently random values. The initial value to seed the PRNG (pseudorandom number generator) is baked-in to the final WebAssembly module, making the sequence of random values for that specific WebAssembly module predictable. An attacker can use the fixed seed to predict random numbers generated by these functions and bypass cryptographic security controls, for example to disclose sensitive data encrypted by functions that use these generators. The problem has been patched in version 0.5.3. No known workarounds exist.

Affected products

fastly js-compute-runtime: before 0.5.3 — fixed in 0.5.3

How to fix

Upgrade to a fixed version: fastly js-compute-runtime 0.5.3. Check the vendor advisory for mitigations.

References

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