CVE-2020-25576: Rand core Unaligned Memory Access Vulnerability

CRITICAL
Advisory Identifier: GHSA-mmc9-pwm7-qj5w
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CVSS 9.8
CWE-704
Published
Advisory Summary

CVE-2020-25576 is a CRITICAL (CVSS 9.8) unaligned memory access vulnerability (CWE-704: Incorrect Type Conversion or Cast) affecting Rand core libraries in the crates.io ecosystem. The issue involves unaligned memory access in rand_core. Remediation is available by upgrading affected packages to version 0.4.2, 0.3.1.

CVE-2020-25576 at a Glance

CVE Identifier CVE-2020-25576
GHSA Identifier GHSA-mmc9-pwm7-qj5w
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-704: Incorrect Type Conversion or Cast
Affected Product Rand core
Package Ecosystem crates.io
Published Date
Last Updated

Security Impact

CVSS: 9.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2020-25576

To remediate this vulnerability, upgrade all affected Rand core dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

rand_core fixed: 0.4.2 
Upgrade rand_core to 0.4.2
rand_core fixed: 0.3.1 
Upgrade rand_core to 0.3.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for rand_core

How to Check if You Are Affected

To determine whether your application is affected by CVE-2020-25576, inspect your project dependencies for Rand core:

inspect dependencies for rand_core

Analyze the terminal output to locate any version of Rand core in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.4.2), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-704: Incorrect Type Conversion or Cast, where the product does not correctly convert an object, resource, or structure from one type to a different type. In Rand core, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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. ### Patches The flaw was corrected by Ralf Jung and Diggory Hardy for `rand_core >= 0.4.2`. ### Workarounds None. ### References See [Rand's changelog](https://github.com/rust-random/rand/blob/master/rand_core/CHANGELOG.md#050---2019-06-06). ### For more information If you have any questions or comments about this advisory, [open an issue in the Rand repository](https://github.com/rust-random/rand/issues/new/choose).

CVE-2020-25576 Affected Rand core Versions

2 component(s)
Fixed Versions:
0.4.20.3.1
Product / Package Ecosystem Affected Versions Fixed Version
rand_core
 crates.io
≥ 0.4.0
< 0.4.2
0.4.2
rand_core
 crates.io
< 0.3.1
0.3.1

References

Rand core Source Repository REPOSITORY
https://github.com/rust-random/rand
GitHub Advisory / Wiki ADVISORY
https://github.com/rust-random/rand/security/advisories/GHSA-mmc9-pwm7-qj5w
Rand core Source Repository REPOSITORY
https://github.com/rust-random/rand/blob/master/rand_core/CHANGELOG.md#050---2019-06-06
rustsec.org/advisories/rustsec-... WEB
https://rustsec.org/advisories/RUSTSEC-2019-0035.html

Frequently Asked Questions

What is CVE-2020-25576?
CVE-2020-25576 is a security vulnerability in Rand core involving Unaligned memory access in rand_core under CWE-704: Incorrect Type Conversion or Cast.
Which Rand core versions are affected?
Affected versions include releases prior to 0.4.2, 0.3.1 across affected packages: rand_core.
What version fixes CVE-2020-25576?
Upgrading to 0.4.2, 0.3.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is rand_core affected?
Yes, rand_core is affected in releases prior to 0.4.2, 0.3.1. Upgrade your dependency to 0.4.2, 0.3.1 or later.
What is the CVSS score of CVE-2020-25576?
CVE-2020-25576 has a CVSS v3.1 base score of 9.8 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2020-25576?
CVE-2020-25576 is classified under CWE-704: Incorrect Type Conversion or Cast (The product does not correctly convert an object, resource, or structure from one type to a different type.).
How can I check crates.io dependencies for CVE-2020-25576?
Run the dependency tree command: 'inspect dependencies for rand_core'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-mmc9-pwm7-qj5w",
  "modified" : "2021-08-18T20:45:24Z",
  "published" : "2021-08-25T20:56:50Z",
  "aliases" : [ "CVE-2020-25576" ],
  "summary" : "Unaligned memory access in rand_core",
  "details" : "### Impact\nAffected 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.\n\n### Patches\nThe flaw was corrected by Ralf Jung and Diggory Hardy for `rand_core >= 0.4.2`.\n\n### Workarounds\nNone.\n\n### References\nSee [Rand's changelog](https://github.com/rust-random/rand/blob/master/rand_core/CHANGELOG.md#050---2019-06-06).\n\n### For more information\nIf you have any questions or comments about this advisory, [open an issue in the Rand repository](https://github.com/rust-random/rand/issues/new/choose).\n\n",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "rand_core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.4.0"
      }, {
        "fixed" : "0.4.2"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "rand_core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.3.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/rust-random/rand/security/advisories/GHSA-mmc9-pwm7-qj5w"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/rust-random/rand"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rust-random/rand/blob/master/rand_core/CHANGELOG.md#050---2019-06-06"
  }, {
    "type" : "WEB",
    "url" : "https://rustsec.org/advisories/RUSTSEC-2019-0035.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-704" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-08-18T20:45:24Z",
    "nvd_published_at" : null
  }
}