CVE-2021-39228: Memory Safety Issue when using patch or merge on state and assign the result back to state

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2021-09-17 · updated 2026-06-17
Weakness: CWE-416

Description

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`.

Affected products

tremor-rs tremor-runtime: from 0.7.2 before 0.11.6 — fixed in 0.11.6

How to fix

Upgrade to a fixed version: tremor-rs tremor-runtime 0.11.6. Check the vendor advisory for mitigations.

References

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