CVE-2021-39228

What it is

Tremor is an event processing system for unstructured data. A vulnerability exists between versions 0.7.2 and 0.11.6. This vulnerability is a memory safety Issue when using `patch` or `merge` on `state` and assign the result back to `state`. In this case, affected versions of Tremor and the tremor-script crate maintains references to memory that might have been freed already. And these memory regions can be accessed by retrieving the `state`, e.g. send it over TCP or HTTP. This requires the Tremor server (or any other program using tremor-script) to execute a tremor-script script that uses the mentioned language construct. The issue has been patched in version 0.11.6 by removing the optimization and always cloning the target expression of a Merge or Patch. If an upgrade is not possible, a possible workaround is to avoid the optimization by introducing a temporary variable and not immediately reassigning to `state`.

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

Exploit odds

1.3% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-09-17 14:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 04:03 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 1.3% in the next 30 days (EPSS).
• Severity: 6.5 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-09-17 14:15 UTC

Last modified

2026-06-17 04:03 UTC

Exploit probability

1.3% · EPSS, next 30 days

Weakness

CWE-416 · Use after free

Record status

Modified

Affected

• Linuxfoundation Tremor < 0.11.6

Attack profile CVSS 3.1 · 6.5

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-39228.md and follow it. Check whether this project is affected by CVE-2021-39228. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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