How severe is CVE-2021-39228?

CVE-2021-39228 has a CVSS score of 9.8/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-39228?

CVE-2021-39228 affects the following packages: tremor-script (crates.io). Ecosystems affected: crates.io.

How do I fix CVE-2021-39228?

Update tremor-script to 0.11.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-39228 is resolved across your whole dependency graph.

How do I detect CVE-2021-39228 in my crates.io dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for tremor-script. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2021-39228 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2021-39228?

O3 pinpoints whether CVE-2021-39228 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2021-39228 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2021-39228, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-39228?

CVE-2021-39228 has an EPSS (Exploit Prediction Scoring System) score of 1.3%, placing it in the 67th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

When was CVE-2021-39228 published, and has it been updated?

CVE-2021-39228 was published on September 17, 2021 and was last updated on April 10, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🦀 crates.io

CVE-2021-39228

CRITICAL

Memory Safety Issue when using patch or merge on state and assign the result back to state

Also known asGHSA-mc22-5q92-8v85

Published

Sep 17, 2021

Updated

Apr 10, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

1 known

EPSS Exploitation Probability

via FIRST.org ↗

1.3%probability of exploitation in next 30 days

Lower Risk67th percentile+0.75%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

1 pkg affected

🦀tremor-script

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.

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 Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🦀crates.io	`tremor-script`	≥ 0.7.3&&< 0.11.6	0.11.6

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Tremor is an event processing system for unstructured data. A vulnerabil…

github.comNVDSep 2021

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for tremor-script. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update tremor-script to 0.11.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-39228 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2021-39228 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2021-39228. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

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

O3 Security · Impact-Aware SCA

Is CVE-2021-39228 in your dependencies?

O3 detects CVE-2021-39228 across crates.io dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works