Summary
Incorrect reliance on Trait memory layout in mopa
The mopa crate redefines the deprecated TraitObject struct from core::raw. This is done to then transmute a reference to a trait object (&dyn Trait for any trait Trait) into this struct and retrieve the data field for the purpose of downcasting. This is used to implement downcast_ref_unchecked(), in terms of which downcast_ref() is also implemented. Same goes for mutable reference downcasting and Box downcasting.
The Rust compiler explicitly reserves the right to change the memory layout of &dyn Trait for any trait Trait. The worst case scenario is that it swaps data and vtable, making an executable location breach and compromisation of ASLR possible, since reads from data would read vtable instead. Likewise, arbitrary code execution is also theoretically possible if reads of vtable generated by the compiler read data instead.
Impact
CVE-2021-45695 has a CVSS score of 9.8 (Critical). The vector is network-reachable, 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. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.
Affected versions
Security releases
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.
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Frequently Asked Questions
- What is CVE-2021-45695? CVE-2021-45695 is a critical-severity security vulnerability in mopa (rust), affecting versions <= 0.2.2. No fixed version is listed yet.
- How severe is CVE-2021-45695? CVE-2021-45695 has a CVSS score of 9.8 (Critical). 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 mopa are affected by CVE-2021-45695? mopa (rust) versions <= 0.2.2 is affected.
- Is there a fix for CVE-2021-45695? No fixed version is listed for CVE-2021-45695 yet. Monitor the advisory for updates and apply mitigations in the interim.
- Is CVE-2021-45695 exploitable, and should I be worried? Whether CVE-2021-45695 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-2021-45695 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.