What is CVE-2025-66627?

CVE-2025-66627 is a high-severity use after free vulnerability in wasmi (rust), affecting versions >= 0.41.0, < 0.41.2. It is fixed in 0.41.2, 0.47.1, 0.51.3, 1.0.1. Memory is accessed after it has been freed, leading to undefined behavior in native code.

How severe is CVE-2025-66627?

CVE-2025-66627 has a CVSS score of 8.4 (High). 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.

Which versions of wasmi are affected by CVE-2025-66627?

wasmi (rust) versions >= 0.41.0, < 0.41.2 is affected.

Is there a fix for CVE-2025-66627?

Yes. CVE-2025-66627 is fixed in 0.41.2, 0.47.1, 0.51.3, 1.0.1. Upgrade to this version or later.

Is CVE-2025-66627 exploitable, and should I be worried?

Whether CVE-2025-66627 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.

What actually determines whether CVE-2025-66627 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.

CVE-2025-66627 in wasmi | Intelligent Application Security

Q: How severe is CVE-2025-66627?

CVE-2025-66627 has a CVSS score of 8.4 (High). 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.

Q: Which versions of wasmi are affected by CVE-2025-66627?

wasmi (rust) versions >= 0.41.0, < 0.41.2 is affected.

Q: Is there a fix for CVE-2025-66627?

Yes. CVE-2025-66627 is fixed in 0.41.2, 0.47.1, 0.51.3, 1.0.1. Upgrade to this version or later.

Q: Is CVE-2025-66627 exploitable, and should I be worried?

Whether CVE-2025-66627 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.

Q: What actually determines whether CVE-2025-66627 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.

Q: How do I fix CVE-2025-66627?

Upgrade: wasmi to 0.41.2 or later, wasmi to 0.47.1 or later, wasmi to 0.51.3 or later, wasmi to 1.0.1 or later.

Summary

A use-after-free vulnerability has been discovered in the linear memory implementation of Wasmi. This issue can be triggered by a WebAssembly module under certain memory growth conditions, potentially leading to memory corruption, information disclosure, or code execution.

Affected Versions

Wasmi v0.41.0 through Wasmi v1.0.0.

Workarounds

Upgrade to the latest patched version of Wasmi.
Consider limiting the maximum linear memory sizes where feasible.

Credits

This vulnerability was discovered by Robert T. Morris (RTM).

Impact

Confidentiality: High, attacker-controlled memory reads possible.
Integrity: High, memory corruption may allow arbitrary writes.
Availability: High, interpreter crashes possible.

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-2025-66627 has a CVSS score of 8.4 (High). The vector is requires local access, no privileges required, and no user interaction. 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 (0.41.2, 0.47.1, 0.51.3, 1.0.1); upgrading removes the vulnerable code path.

Affected versions

wasmi (>= 0.41.0, < 0.41.2) wasmi (>= 0.42.0, < 0.47.1) wasmi (>= 0.50.0, < 0.51.3) wasmi (>= 1.0.0, < 1.0.1)

Security releases

wasmi → 0.41.2 (rust) wasmi → 0.47.1 (rust) wasmi → 0.51.3 (rust) wasmi → 1.0.1 (rust)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

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. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

See it in your environment

Remediation advice

Upgrade the following packages to resolve this vulnerability:

wasmi to 0.41.2 or later; wasmi to 0.47.1 or later; wasmi to 0.51.3 or later; wasmi to 1.0.1 or later

Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.

Frequently Asked Questions

What is CVE-2025-66627? CVE-2025-66627 is a high-severity use after free vulnerability in wasmi (rust), affecting versions >= 0.41.0, < 0.41.2. It is fixed in 0.41.2, 0.47.1, 0.51.3, 1.0.1. Memory is accessed after it has been freed, leading to undefined behavior in native code.
How severe is CVE-2025-66627? CVE-2025-66627 has a CVSS score of 8.4 (High). 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.
Which versions of wasmi are affected by CVE-2025-66627? wasmi (rust) versions >= 0.41.0, < 0.41.2 is affected.
Is there a fix for CVE-2025-66627? Yes. CVE-2025-66627 is fixed in 0.41.2, 0.47.1, 0.51.3, 1.0.1. Upgrade to this version or later.
Is CVE-2025-66627 exploitable, and should I be worried? Whether CVE-2025-66627 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
What actually determines whether CVE-2025-66627 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.
How do I fix CVE-2025-66627?
- Upgrade wasmi to 0.41.2 or later
- Upgrade wasmi to 0.47.1 or later
- Upgrade wasmi to 0.51.3 or later
- Upgrade wasmi to 1.0.1 or later

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