@fastly/js-compute has a use-after-free in some host call implementations

MEDIUM 5.3CVE-2024-38375 · GHSA-mp3g-vpm9-9vqv · Published 26/06/2024 · updated 17/06/2026

In short

CVE-2024-38375 is a MEDIUM (CVSS 5.3) vulnerability affecting @fastly/js-compute.
Chance of exploitation in the next 30 days (EPSS): 0.27%, higher than 18.6% of all vulnerabilities.
Fix: update to 3.16.0 or later.

Package	Affected versions	Patched versions
@fastly/js-compute npm	`≥ 3.0.0, < 3.16.0`	`3.16.0`

Description

Impact

The implementation of the following functions were determined to include a use-after-free bug:

FetchEvent.client.tlsCipherOpensslName
FetchEvent.client.tlsProtocol
FetchEvent.client.tlsClientCertificate
FetchEvent.client.tlsJA3MD5
FetchEvent.client.tlsClientHello
CacheEntry.prototype.userMetadata of the fastly:cache subsystem
Device.lookup of the fastly:device subsystem

This bug could allow for an unintended data leak if the result of the preceding functions were sent anywhere else, and often results in a Compute service crash causing an HTTP 500 error to be returned. As all requests to Compute are isolated from one another, the only data at risk is data present for a single request.

Patches

This bug has been fixed in version 3.16.0 of the @fastly/js-compute package.

Workarounds

There are no workarounds for this bug, any use of the affected functions introduces the possibility of a data leak or crash in guest code.

NVD description

@fastly/js-compute is a JavaScript SDK and runtime for building Fastly Compute applications. The implementation of several functions were determined to include a use-after-free bug. This bug could allow for unintended data loss if the result of the preceding functions were sent anywhere else, and often results in a guest trap causing services to return a 500. This bug has been fixed in version 3.16.0 of the `@fastly/js-compute` package.

References

fastly/js-compute-runtime security advisory · WEB
nvd.nist.gov/vuln/detail/CVE-2024-38375 · ADVISORY
fastly/js-compute-runtime commit 4e16641 · WEB
fastly/js-compute-runtime · PACKAGE

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Package

Affected versions

Patched versions

@fastly/js-compute

npm

≥ 3.0.0, < 3.16.0

3.16.0

Description

Impact

The implementation of the following functions were determined to include a use-after-free bug:

FetchEvent.client.tlsCipherOpensslName
FetchEvent.client.tlsProtocol
FetchEvent.client.tlsClientCertificate
FetchEvent.client.tlsJA3MD5
FetchEvent.client.tlsClientHello
CacheEntry.prototype.userMetadata of the fastly:cache subsystem
Device.lookup of the fastly:device subsystem

Patches

This bug has been fixed in version 3.16.0 of the @fastly/js-compute package.

Workarounds

There are no workarounds for this bug, any use of the affected functions introduces the possibility of a data leak or crash in guest code.

NVD description