CVE-2021-25900: Buffer overflow in SmallVec :insert_many Vulnerability

CRITICAL
Advisory Identifier: GHSA-43w2-9j62-hq99
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CVSS 9.8
CWE-787
Published
Advisory Summary

CVE-2021-25900 is a CRITICAL (CVSS 9.8) :insert_many vulnerability (CWE-787: Out-of-bounds Write) affecting Buffer overflow in SmallVec libraries in the crates.io ecosystem. The issue involves :insert_many. Remediation is available by upgrading affected packages to version 0.6.14, 1.6.1.

CVE-2021-25900 at a Glance

CVE Identifier CVE-2021-25900
GHSA Identifier GHSA-43w2-9j62-hq99
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-787: Out-of-bounds Write
Affected Product Buffer overflow in 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:3.1/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-2021-25900

To remediate this vulnerability, upgrade all affected Buffer overflow in 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: 0.6.14 
Upgrade smallvec to 0.6.14
smallvec fixed: 1.6.1 
Upgrade smallvec to 1.6.1
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 smallvec

How to Check if You Are Affected

To determine whether your application is affected by CVE-2021-25900, inspect your project dependencies for Buffer overflow in SmallVec:

inspect dependencies for smallvec

Analyze the terminal output to locate any version of Buffer overflow in SmallVec in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.6.14), 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-787: Out-of-bounds Write, where the product writes data past the end, or before the beginning, of the intended buffer. In Buffer overflow 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

A bug in the SmallVec::insert_many method caused it to allocate a buffer that was smaller than needed. It then wrote past the end of the buffer, causing a buffer overflow and memory corruption on the heap. This bug was only triggered if the iterator passed to insert_many yielded more items than the lower bound returned from its size_hint method. The flaw was corrected in smallvec 0.6.14 and 1.6.1, by ensuring that additional space is always reserved for each item inserted. The fix also simplified the implementation of insert_many to use less unsafe code, so it is easier to verify its correctness.

CVE-2021-25900 Affected Buffer overflow in SmallVec Versions

2 component(s)
Fixed Versions:
0.6.141.6.1
Product / Package Ecosystem Affected Versions Fixed Version
smallvec
 crates.io
≥ 0.6.3
< 0.6.14
0.6.14
smallvec
 crates.io
≥ 1.0.0
< 1.6.1
1.6.1

References

NVD — CVE-2021-25900 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-25900
Buffer overflow in SmallVec Source Repository REPOSITORY
https://github.com/servo/rust-smallvec/issues/252
Security Fix Commit FIX COMMIT
https://github.com/servo/rust-smallvec/commit/5757ac500d4e544485d796b542e4e589749c291b
Security Fix Commit FIX COMMIT
https://github.com/servo/rust-smallvec/commit/9998ba0694a6b51aa6604748b00b6a98f0a0039e
Buffer overflow in SmallVec Source Repository REPOSITORY
https://github.com/servo/rust-smallvec
rustsec.org/advisories/rustsec-... WEB
https://rustsec.org/advisories/RUSTSEC-2021-0003.html

Frequently Asked Questions

What is CVE-2021-25900?
CVE-2021-25900 is a security vulnerability in Buffer overflow in SmallVec involving :insert_many under CWE-787: Out-of-bounds Write.
Which Buffer overflow in SmallVec versions are affected?
Affected versions include releases prior to 0.6.14, 1.6.1 across affected packages: smallvec.
What version fixes CVE-2021-25900?
Upgrading to 0.6.14, 1.6.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is smallvec affected?
Yes, smallvec is affected in releases prior to 0.6.14, 1.6.1. Upgrade your dependency to 0.6.14, 1.6.1 or later.
What is the CVSS score of CVE-2021-25900?
CVE-2021-25900 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-2021-25900?
CVE-2021-25900 is classified under CWE-787: Out-of-bounds Write (The product writes data past the end, or before the beginning, of the intended buffer.).
How can I check crates.io dependencies for CVE-2021-25900?
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-43w2-9j62-hq99",
  "modified" : "2023-06-13T20:51:42Z",
  "published" : "2022-05-24T17:40:21Z",
  "aliases" : [ "CVE-2021-25900" ],
  "summary" : "Buffer overflow in SmallVec::insert_many",
  "details" : "A bug in the SmallVec::insert_many method caused it to allocate a buffer that was smaller than needed. It then wrote past the end of the buffer, causing a buffer overflow and memory corruption on the heap. This bug was only triggered if the iterator passed to insert_many yielded more items than the lower bound returned from its size_hint method.\n\nThe flaw was corrected in smallvec 0.6.14 and 1.6.1, by ensuring that additional space is always reserved for each item inserted. The fix also simplified the implementation of insert_many to use less unsafe code, so it is easier to verify its correctness.",
  "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" : [ {
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      "ecosystem" : "crates.io",
      "name" : "smallvec"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.6.3"
      }, {
        "fixed" : "0.6.14"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "smallvec"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
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      }, {
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      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-25900"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/servo/rust-smallvec/issues/252"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/servo/rust-smallvec/commit/5757ac500d4e544485d796b542e4e589749c291b"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/servo/rust-smallvec/commit/9998ba0694a6b51aa6604748b00b6a98f0a0039e"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/servo/rust-smallvec"
  }, {
    "type" : "WEB",
    "url" : "https://rustsec.org/advisories/RUSTSEC-2021-0003.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-787" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-06-17T00:20:48Z",
    "nvd_published_at" : "2021-01-26T18:16:00Z"
  }
}