CVE-2018-20991: Smallvec Double Free Vulnerability

CRITICAL
Advisory Identifier: GHSA-rxr4-x558-x7hw
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CVSS 9.8
CWE-415
Published
Advisory Summary

CVE-2018-20991 is a CRITICAL (CVSS 9.8) double free vulnerability (CWE-415: Double Free) affecting Smallvec libraries in the crates.io ecosystem. The issue involves double free in smallvec. Remediation is available by upgrading affected packages to version 0.6.3.

CVE-2018-20991 at a Glance

CVE Identifier CVE-2018-20991
GHSA Identifier GHSA-rxr4-x558-x7hw
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-415: Double Free
Affected Product Smallvec
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:3.0/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-2018-20991

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

smallvec fixed: 0.6.3 
Upgrade smallvec to 0.6.3
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 smallvec

How to Check if You Are Affected

To determine whether your application is affected by CVE-2018-20991, inspect your project dependencies for Smallvec:

inspect dependencies for smallvec

Analyze the terminal output to locate any version of Smallvec in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.6.3), 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-415: Double Free, where the product calls free() twice on the same memory address. In Smallvec, 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

If an iterator passed to SmallVec::insert_many panicked in Iterator::next, destructors were run during unwinding while the vector was in an inconsistent state, possibly causing a double free (a destructor running on two copies of the same value). This is fixed in smallvec 0.6.3 by ensuring that the vector's length is not updated to include moved items until they have been removed from their original positions. Items may now be leaked if Iterator::next panics, but they will not be dropped more than once.

CVE-2018-20991 Affected Smallvec Versions

1 component(s)
Fixed Versions:
0.6.3
Product / Package Ecosystem Affected Versions Fixed Version
smallvec
 crates.io
≥ 0.3.2
< 0.6.3
0.6.3

References

NVD — CVE-2018-20991 NVD
https://nvd.nist.gov/vuln/detail/CVE-2018-20991
Smallvec Source Repository REPOSITORY
https://github.com/servo/rust-smallvec/issues/96
Smallvec Source Repository REPOSITORY
https://github.com/servo/rust-smallvec
rustsec.org/advisories/rustsec-... WEB
https://rustsec.org/advisories/RUSTSEC-2018-0003.html

Frequently Asked Questions

What is CVE-2018-20991?
CVE-2018-20991 is a security vulnerability in Smallvec involving Double free in smallvec under CWE-415: Double Free.
Which Smallvec versions are affected?
Affected versions include releases prior to 0.6.3 across affected packages: smallvec.
What version fixes CVE-2018-20991?
Upgrading to 0.6.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is smallvec affected?
Yes, smallvec is affected in releases prior to 0.6.3. Upgrade your dependency to 0.6.3 or later.
What is the CVSS score of CVE-2018-20991?
CVE-2018-20991 has a CVSS v3.1 base score of 9.8 (CRITICAL) with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2018-20991?
CVE-2018-20991 is classified under CWE-415: Double Free (The product calls free() twice on the same memory address.).
How can I check crates.io dependencies for CVE-2018-20991?
Run the dependency tree command: 'inspect dependencies for smallvec'. 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-rxr4-x558-x7hw",
  "modified" : "2023-06-13T20:58:32Z",
  "published" : "2021-08-25T20:42:54Z",
  "aliases" : [ "CVE-2018-20991" ],
  "summary" : "Double free in smallvec",
  "details" : "If an iterator passed to SmallVec::insert_many panicked in Iterator::next, destructors were run during unwinding while the vector was in an inconsistent state, possibly causing a double free (a destructor running on two copies of the same value).\n\nThis is fixed in smallvec 0.6.3 by ensuring that the vector's length is not updated to include moved items until they have been removed from their original positions. Items may now be leaked if Iterator::next panics, but they will not be dropped more than once.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "smallvec"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.3.2"
      }, {
        "fixed" : "0.6.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2018-20991"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/servo/rust-smallvec/issues/96"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/servo/rust-smallvec"
  }, {
    "type" : "WEB",
    "url" : "https://rustsec.org/advisories/RUSTSEC-2018-0003.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-415" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-08-19T21:25:34Z",
    "nvd_published_at" : null
  }
}