CVE-2024-38375

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

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.

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.

Memory is accessed after it has been freed, leading to undefined behavior in native code. Typical impact: memory corruption, crash, or potential code execution.

CVE-2024-38375 has a CVSS score of 5.3 (Medium). The vector is network-reachable, high privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.16.0); upgrading removes the vulnerable code path.

Kodem intelligence

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

1. What is CVE-2024-38375? CVE-2024-38375 is a medium-severity use after free vulnerability in @fastly/js-compute (npm), affecting versions >= 3.0.0, < 3.16.0. It is fixed in 3.16.0. Memory is accessed after it has been freed, leading to undefined behavior in native code.
2. How severe is CVE-2024-38375? CVE-2024-38375 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of @fastly/js-compute are affected by CVE-2024-38375? @fastly/js-compute (npm) versions >= 3.0.0, < 3.16.0 is affected.
4. Is there a fix for CVE-2024-38375? Yes. CVE-2024-38375 is fixed in 3.16.0. Upgrade to this version or later.
5. Is CVE-2024-38375 exploitable, and should I be worried? Whether CVE-2024-38375 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2024-38375 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2024-38375? Upgrade @fastly/js-compute to 3.16.0 or later.

Other vulnerabilities in @fastly/js-compute