External risk intelligence

Rust rand Crate Alignment Constraint Mishandling

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2020-25576

This vulnerability exists in a Rust programming language library (crate) used during software development and build-time. It is a dependency component integrated into applications rather than a standalone, internet-facing service or appliance. Consequently, it lacks direct exposure to the public internet in typical deployment scenarios.

Rust Random Rand

before 0.4.2

Halo Surface Signal: 1 out of 5 — much less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This CVE involves a flaw in a Rust programming library that manages random number generation. The issue arises from how byte data is converted to integers, potentially causing problems with data integrity and system stability. While this flaw exists in a development tool, its relevance depends on whether your organization uses this specific library in its software development processes.

Alignment issue in a Rust programming library.
Impacts software development, not direct operations.
Confirm use to assess potential relevance.

Attack Path

How an attacker could exploit the issue

An attacker could leverage a flaw in the `rand_core` crate when handling byte slices, which is used in Rust software development. This misaligned casting of data can lead to critical security issues if successfully triggered.

Entry condition: Code vulnerability in a dependency.
Trigger point: Casting byte slices to integer slices.
Resulting risk: Widespread system compromise.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability in the `rand_core` crate could allow an attacker to corrupt internal state when converting byte slices to integer slices, potentially impacting the integrity and availability of applications that rely on this library for random number generation.

Corrupted randomness generation.
Mishandling alignment constraints.
Compromised application integrity.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability in the `rand_core` crate, a component used in Rust software development, requires attention from teams responsible for the software supply chain and application development. The first practical step is to identify all applications and services that utilize this dependency, confirm their exposure and business criticality, and then locate the accountable development or platform team to plan remediation.

Application and platform teams own resolution.
Verify affected applications and their exposure.
Plan remediation based on risk and criticality.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is the rand crate?

The rand crate is a foundational library for the Rust programming language used to generate random numbers. Developers integrate this component into their software to handle tasks requiring randomness, such as cryptography, simulations, or randomized algorithms. It functions as a building block for applications rather than as a standalone service or end-user program.

What does CWE-704 mean for CVE-2020-25576?

CWE-704 refers to incorrect type conversion or casting. In the context of CVE-2020-25576, the library improperly converts byte slices into integer slices without respecting hardware memory alignment rules. This technical oversight can confuse the computer's memory management, potentially allowing data to be misread or corrupted during processing.

How is this vulnerability triggered?

The flaw is triggered when the library performs a specific type cast of byte slices to integer slices. It is important to note that simply having the library present in a codebase is not enough to trigger the bug; the code must actually execute the specific, misaligned conversion path. If your application logic does not invoke the affected casting operation, that specific code path is not triggered.

Should I be concerned about CVE-2020-25576?

Halo Surface Signal indicates that because this is a developer library rather than an internet-facing service, it is very unlikely to have direct exposure to the public internet. Concern should be focused on whether your internally developed software uses older versions of this library, as the risk is tied to how your specific applications are built and what data they process.

What are the first steps to address this?

Your first step is to perform a software bill of materials analysis to identify if any of your applications or services include the rand_core crate version 0.4.1 or older. Once identified, coordinate with your internal development or platform engineering teams. They must verify if the application is affected and plan to update the dependency to a secure version in the next development cycle.

References

rustsec.org/advisories/RUSTSEC-2019-0035.html

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.