Summary
Unaligned memory access in rand_core
Workarounds
None.
References
See Rand's changelog.
For more information
If you have any questions or comments about this advisory, open an issue in the Rand repository.
Impact
Affected versions of this crate violated alignment when casting byte slices to integer slices, resulting in undefined behavior. rand_core::BlockRng::next_u64 and rand_core::BlockRng::fill_bytes are affected.
CVE-2020-25576 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. A fixed version is available (0.4.2, 0.3.1); upgrading removes the vulnerable code path.
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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The flaw was corrected by Ralf Jung and Diggory Hardy for rand_core >= 0.4.2.
Frequently Asked Questions
- What is CVE-2020-25576? CVE-2020-25576 is a critical-severity security vulnerability in rand_core (rust), affecting versions >= 0.4.0, < 0.4.2. It is fixed in 0.4.2, 0.3.1.
- How severe is CVE-2020-25576? CVE-2020-25576 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 rand_core are affected by CVE-2020-25576? rand_core (rust) versions >= 0.4.0, < 0.4.2 is affected.
- Is there a fix for CVE-2020-25576? Yes. CVE-2020-25576 is fixed in 0.4.2, 0.3.1. Upgrade to this version or later.
- Is CVE-2020-25576 exploitable, and should I be worried? Whether CVE-2020-25576 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-2020-25576 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-2020-25576?
- Upgrade
rand_coreto 0.4.2 or later - Upgrade
rand_coreto 0.3.1 or later
- Upgrade