CVE-2022-39218Network attack vector

Sensitive-data disclosure via compile-time fixed PRNG seed

Published Sep 20, 2022 · Updated Apr 23, 2025

Predictable randomness in Fastly js-compute-runtime before 0.5.3 allows attackers with a generated WebAssembly module to disclose sensitive data. The build initializes the pseudorandom generator before Wizer snapshots the runtime, embedding its seed so Math.random and crypto.getRandomValues produce a predictable sequence. Exploitation requires access to the same module and affects only application controls that rely on those functions, including encryption that can expose protected data.

CVSS severity7.5
High
EPSS probability0.83%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Predictable randomness in Fastly js-compute-runtime before 0.5.3 allows attackers with a generated WebAssembly module to disclose sensitive data. The build initializes the pseudorandom generator before Wizer snapshots the runtime, embedding its seed so Math.random and crypto.getRandomValues produce a predictable sequence. Exploitation requires access to the same module and affects only application controls that rely on those functions, including encryption that can expose protected data.

The record

CVE
CVE-2022-39218
Published
Sep 20, 2022
Updated
Apr 23, 2025
Vendor
Fastly
Product
Fastly js-compute-runtime
Classifications
CWE-335
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 20, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 23, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.5.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Fastly · Fastly js-compute-runtimeversion=< 0.5.3

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-335Incorrect Usage of Seeds in Pseudo-Random Number Generator (PRNG)

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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