CVE-2021-21401: Nanopb Nanopb Vulnerable To Invalid Free() Vulnerability

HIGH
Advisory Identifier: GHSA-7mv5-5mxh-qg88
Share
CVSS 7.1
CWE-763
Published
Advisory Summary

CVE-2021-21401 is a HIGH (CVSS 7.1) nanopb vulnerable to invalid free() vulnerability (CWE-763: Release of Invalid Pointer or Reference) affecting Nanopb libraries in the PyPI ecosystem. The issue involves nanopb vulnerable to invalid free() call with oneofs and pb_enable_malloc. Remediation is available by upgrading affected packages to version 0.3.9.8, 0.4.5.

CVE-2021-21401 at a Glance

CVE Identifier CVE-2021-21401
GHSA Identifier GHSA-7mv5-5mxh-qg88
Severity HIGH
CVSS v3.1 Base Score 7.1
CWE Classification CWE-763: Release of Invalid Pointer or Reference
Affected Product Nanopb
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.1

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

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

How to Fix CVE-2021-21401

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

nanopb fixed: 0.3.9.8 
pip install nanopb>=0.3.9.8
nanopb fixed: 0.4.5 
pip install nanopb>=0.4.5
Verify Direct and Transitive Dependencies

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

pip show nanopb

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2021-21401, inspect your installed packages using pip:

pip show nanopb

Analyze the terminal output to locate any version of Nanopb in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.3.9.8), your application is affected.

Note: The pip show nanopb command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-763: Release of Invalid Pointer or Reference, where the product attempts to return a memory resource to the system, but it calls the wrong release function or calls the appropriate release function incorrectly. In Nanopb, 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 Decoding a specifically formed message can cause invalid `free()` or `realloc()` calls if the message type contains an `oneof` field, and the `oneof` directly contains both a pointer field and a non-pointer field. If the message data first contains the non-pointer field and then the pointer field, the data of the non-pointer field is incorrectly treated as if it was a pointer value. Such message data rarely occurs in normal messages, but it is a concern when untrusted data is parsed. ### Patches Preliminary patch is available on git for [0.4.x](https://github.com/nanopb/nanopb/commit/e2f0ccf939d9f82931d085acb6df8e9a182a4261) and [0.3.x](https://github.com/nanopb/nanopb/commit/4a375a560651a86726e5283be85a9231fd0efe9c) branches. The fix will be released in versions 0.3.9.8 and 0.4.5 once testing has been completed. ### Workarounds Following workarounds are available: * Set the option `no_unions` for the oneof field. This will generate fields as separate instead of C union, and avoids triggering the problematic code. * Set the type of all fields inside the oneof to `FT_POINTER`. This ensures that the data contained inside the `union` is always a valid pointer. * Heap implementations that guard against invalid `free()` provide a partial mitigation. Depending on the message type, the pointer value may be attacker controlled and can be used to bypass heap protections. ### References Bug report: https://github.com/nanopb/nanopb/issues/647 ### For more information If you have any questions or comments about this advisory, comment on the bug report linked above.

CVE-2021-21401 Affected Nanopb Versions

2 component(s)
Fixed Versions:
0.3.9.80.4.5
Product / Package Ecosystem Affected Versions Fixed Version
nanopb
pypi/nanopb
PyPI
≥ 0.3.2
< 0.3.9.8
0.3.9.8
nanopb
pypi/nanopb
PyPI
≥ 0.4.0
< 0.4.5
0.4.5

References

GitHub Advisory / Wiki ADVISORY
https://github.com/nanopb/nanopb/security/advisories/GHSA-7mv5-5mxh-qg88
NVD — CVE-2021-21401 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-21401
Nanopb Source Repository REPOSITORY
https://github.com/nanopb/nanopb/issues/647
Security Fix Commit FIX COMMIT
https://github.com/nanopb/nanopb/commit/4a375a560651a86726e5283be85a9231fd0efe9c
Security Fix Commit FIX COMMIT
https://github.com/nanopb/nanopb/commit/e2f0ccf939d9f82931d085acb6df8e9a182a4261
Nanopb Source Repository REPOSITORY
https://github.com/nanopb/nanopb
Nanopb Source Repository REPOSITORY
https://github.com/nanopb/nanopb/blob/c9124132a604047d0ef97a09c0e99cd9bed2c818/CHANGELOG.txt#L1
Nanopb Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/nanopb/PYSEC-2021-432.yaml

Frequently Asked Questions

What is CVE-2021-21401?
CVE-2021-21401 is a security vulnerability in Nanopb involving nanopb vulnerable to invalid free() call with oneofs and PB_ENABLE_MALLOC under CWE-763: Release of Invalid Pointer or Reference.
Which Nanopb versions are affected?
Affected versions include releases prior to 0.3.9.8, 0.4.5 across affected packages: nanopb.
What version fixes CVE-2021-21401?
Upgrading to 0.3.9.8, 0.4.5 (or the latest patched release for your respective branch) resolves the vulnerability.
Is nanopb affected?
Yes, nanopb is affected in releases prior to 0.3.9.8, 0.4.5. Upgrade your dependency to 0.3.9.8, 0.4.5 or later.
What is the CVSS score of CVE-2021-21401?
CVE-2021-21401 has a CVSS v3.1 base score of 7.1 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L.
What CWE is associated with CVE-2021-21401?
CVE-2021-21401 is classified under CWE-763: Release of Invalid Pointer or Reference (The product attempts to return a memory resource to the system, but it calls the wrong release function or calls the appropriate release function incorrectly.).
How can I check PyPI dependencies for CVE-2021-21401?
Run the dependency tree command: 'pip show nanopb'. 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-7mv5-5mxh-qg88",
  "modified" : "2024-08-30T18:45:41Z",
  "published" : "2024-08-30T18:45:41Z",
  "aliases" : [ "CVE-2021-21401" ],
  "summary" : "nanopb vulnerable to invalid free() call with oneofs and PB_ENABLE_MALLOC",
  "details" : "### Impact\nDecoding a specifically formed message can cause invalid `free()` or `realloc()` calls if the message type contains an `oneof` field, and the `oneof` directly contains both a pointer field and a non-pointer field. If the message data first contains the non-pointer field and then the pointer field, the data of the non-pointer field is incorrectly treated as if it was a pointer value. Such message data rarely occurs in normal messages, but it is a concern when untrusted data is parsed.\n\n### Patches\nPreliminary patch is available on git for [0.4.x](https://github.com/nanopb/nanopb/commit/e2f0ccf939d9f82931d085acb6df8e9a182a4261) and [0.3.x](https://github.com/nanopb/nanopb/commit/4a375a560651a86726e5283be85a9231fd0efe9c) branches. The fix will be released in versions 0.3.9.8 and 0.4.5 once testing has been completed.\n\n### Workarounds\nFollowing workarounds are available:\n* Set the option `no_unions` for the oneof field. This will generate fields as separate instead of C union, and avoids triggering the problematic code.\n* Set the type of all fields inside the oneof to `FT_POINTER`. This ensures that the data contained inside the `union` is always a valid pointer.\n* Heap implementations that guard against invalid `free()` provide a partial mitigation. Depending on the message type, the pointer value may be attacker controlled and can be used to bypass heap protections.\n\n### References\nBug report: https://github.com/nanopb/nanopb/issues/647\n\n### For more information\nIf you have any questions or comments about this advisory, comment on the bug report linked above.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "nanopb"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.3.2"
      }, {
        "fixed" : "0.3.9.8"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "nanopb"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.4.0"
      }, {
        "fixed" : "0.4.5"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/nanopb/nanopb/security/advisories/GHSA-7mv5-5mxh-qg88"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-21401"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nanopb/nanopb/issues/647"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nanopb/nanopb/commit/4a375a560651a86726e5283be85a9231fd0efe9c"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nanopb/nanopb/commit/e2f0ccf939d9f82931d085acb6df8e9a182a4261"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/nanopb/nanopb"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nanopb/nanopb/blob/c9124132a604047d0ef97a09c0e99cd9bed2c818/CHANGELOG.txt#L1"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/nanopb/PYSEC-2021-432.yaml"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-763" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-08-30T18:45:41Z",
    "nvd_published_at" : "2021-03-23T18:15:00Z"
  }
}