CVE-2021-29510: Pydantic Use Of "infinity" As An Vulnerability

MODERATE
Advisory Identifier: GHSA-5jqp-qgf6-3pvh
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CVSS 3.3
CWE-835
Published
Advisory Summary

CVE-2021-29510 is a MODERATE (CVSS 3.3) use of "infinity" as an vulnerability (CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop')) affecting Pydantic libraries in the PyPI ecosystem. The issue involves use of "infinity" as an input to datetime and date fields causes infinite loop in pydantic. Remediation is available by upgrading affected packages to version 1.6.2, 1.8.2, 1.7.4.

CVE-2021-29510 at a Glance

CVE Identifier CVE-2021-29510
GHSA Identifier GHSA-5jqp-qgf6-3pvh
Severity MODERATE
CVSS v3.1 Base Score 3.3
CWE Classification CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop')
Affected Product Pydantic
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 3.3

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

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

How to Fix CVE-2021-29510

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

pydantic fixed: 1.6.2 
pip install pydantic>=1.6.2
pydantic fixed: 1.8.2 
pip install pydantic>=1.8.2
pydantic fixed: 1.7.4 
pip install pydantic>=1.7.4
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 pydantic

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2021-29510, inspect your installed packages using pip:

pip show pydantic

Analyze the terminal output to locate any version of Pydantic in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.6.2), your application is affected.

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

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop'), where the product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop. In Pydantic, 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 Passing either 'infinity', 'inf' or float('inf') (or their negatives) to datetime or date fields causes validation to run forever with 100% CPU usage (on one CPU). Patches Pydantic is be patched with fixes available in the following versions: v1.8.2 v1.7.4 v1.6.2 All these versions are available on pypi, and will be available on conda-forge soon. See the changelog for details. Workarounds If you absolutely can't upgrade, you can work around this risk using a validator to catch these values, brief demo: from datetime import date from pydantic import BaseModel, validator class DemoModel(BaseModel): date_of_birth: date @validator('date_of_birth', pre=True) def skip_infinite_values(cls, v): try: seconds = float(v) except (ValueError, TypeError): return v else: if seconds == float('inf'): return date.max elif seconds == float('-inf'): return date.min else: return seconds Note: this is not an ideal solution (in particular you'll need a slightly different function for datetimes), instead of a hack like this you should upgrade pydantic. If you are not using v1.8.x, v1.7.x or v1.6.x and are unable to upgrade to a fixed version of pydantic, please create an issue requesting a back-port, and we will endeavour to release a patch for earlier versions of pydantic. References This was fixed in commit 7e83fdd.

CVE-2021-29510 Affected Pydantic Versions

3 component(s)
Fixed Versions:
1.6.21.8.21.7.4
Product / Package Ecosystem Affected Versions Fixed Version
pydantic
pypi/pydantic
PyPI
< 1.6.2
1.6.2
pydantic
pypi/pydantic
PyPI
≥ 1.8
< 1.8.2
1.8.2
pydantic
pypi/pydantic
PyPI
≥ 1.7
< 1.7.4
1.7.4

References

GitHub Advisory / Wiki ADVISORY
https://github.com/samuelcolvin/pydantic/security/advisories/GHSA-5jqp-qgf6-3pvh
NVD — CVE-2021-29510 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-29510
Security Fix Commit FIX COMMIT
https://github.com/pydantic/pydantic/commit/1c24f1d74ba95ea985b50bdc001ce96c813229aa
Security Fix Commit FIX COMMIT
https://github.com/pydantic/pydantic/commit/80e0dd3f752bef145dce12f160d262bb40ec8d47
Security Fix Commit FIX COMMIT
https://github.com/pydantic/pydantic/commit/bdde15b7b947c94ca00fd6eb92da8db390a13520
Security Fix Commit FIX COMMIT
https://github.com/samuelcolvin/pydantic/commit/7e83fdd2563ffac081db7ecdf1affa65ef38c468
Pydantic Source Repository REPOSITORY
https://github.com/pydantic/pydantic
Pydantic Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/pydantic/PYSEC-2021-47.yaml
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Frequently Asked Questions

What is CVE-2021-29510?
CVE-2021-29510 is a security vulnerability in Pydantic involving Use of "infinity" as an input to datetime and date fields causes infinite loop in pydantic under CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop').
Which Pydantic versions are affected?
Affected versions include releases prior to 1.6.2, 1.8.2, 1.7.4 across affected packages: pydantic.
What version fixes CVE-2021-29510?
Upgrading to 1.6.2, 1.8.2, 1.7.4 (or the latest patched release for your respective branch) resolves the vulnerability.
Is pydantic affected?
Yes, pydantic is affected in releases prior to 1.6.2, 1.8.2, 1.7.4. Upgrade your dependency to 1.6.2, 1.8.2, 1.7.4 or later.
What is the CVSS score of CVE-2021-29510?
CVE-2021-29510 has a CVSS v3.1 base score of 3.3 (MODERATE) with vector string CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L.
What CWE is associated with CVE-2021-29510?
CVE-2021-29510 is classified under CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop') (The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.).
How can I check PyPI dependencies for CVE-2021-29510?
Run the dependency tree command: 'pip show pydantic'. 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-5jqp-qgf6-3pvh",
  "modified" : "2026-06-09T13:01:00Z",
  "published" : "2021-05-13T20:23:17Z",
  "aliases" : [ "CVE-2021-29510" ],
  "summary" : "Use of \"infinity\" as an input to datetime and date fields causes infinite loop in pydantic",
  "details" : "Impact\n\nPassing either 'infinity', 'inf' or float('inf') (or their negatives) to datetime or date fields causes validation to run forever with 100% CPU usage (on one CPU).\nPatches\n\nPydantic is be patched with fixes available in the following versions:\n\n    v1.8.2\n    v1.7.4\n    v1.6.2\n\nAll these versions are available on pypi, and will be available on conda-forge soon.\n\nSee the changelog for details.\nWorkarounds\n\nIf you absolutely can't upgrade, you can work around this risk using a validator to catch these values, brief demo:\n\nfrom datetime import date\nfrom pydantic import BaseModel, validator\n\nclass DemoModel(BaseModel):\n    date_of_birth: date\n\n    @validator('date_of_birth', pre=True)\n    def skip_infinite_values(cls, v):\n        try:\n            seconds = float(v)\n        except (ValueError, TypeError):\n            return v\n        else:\n            if seconds == float('inf'):\n                return date.max\n            elif seconds == float('-inf'):\n                return date.min\n            else:\n                return seconds\n\nNote: this is not an ideal solution (in particular you'll need a slightly different function for datetimes), instead of a hack like this you should upgrade pydantic.\n\nIf you are not using v1.8.x, v1.7.x or v1.6.x and are unable to upgrade to a fixed version of pydantic, please create an issue requesting a back-port, and we will endeavour to release a patch for earlier versions of pydantic.\nReferences\n\nThis was fixed in commit 7e83fdd.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N"
  } ],
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    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-29510"
  }, {
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    "url" : "https://github.com/pydantic/pydantic/commit/1c24f1d74ba95ea985b50bdc001ce96c813229aa"
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  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/S2HT266L6Q7H6ICP7DFGXOGBJHNNKMKB"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/UEFWM7DYKD2ZHE7R5YT5EQWJPV4ZKYRB"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/UMKAJX4O6IGBBCE32CO2G7PZQCCQSBLV"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-835" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-05-13T18:54:35Z",
    "nvd_published_at" : "2021-05-13T19:15:00Z"
  }
}