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Medium, CVSS 5.3amended

Use of "infinity" as an input to datetime and date fields causes infinite loop in pydantic

CVE-2021-29510GHSA-5jqp-qgf6-3pvh

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (pydantic 1.8.2, 1.7.4, 1.6.2), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • PyPI pydantic

    Affected
    < 1.6.2>= 1.8, < 1.8.2>= 1.7, < 1.7.4
    Fixed in
    1.7.4, 1.8.2, 1.6.2

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
5.3 · 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 · score source
EPSS
  • CVE-2021-29510: 0.97% estimated exploitation activity in the next 30 days; percentile 62.14 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

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): dateofbirth: date @validator('dateofbirth', pre=True) def skipinfinitevalues(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…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-5jqp-qgf6-3pvh

  2. Revision 2 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 1 · created ·

    Published from osv record GHSA-5jqp-qgf6-3pvh

Agent brief

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# Patch Next advisory brief: CVE-2021-29510

Advisory: Use of "infinity" as an input to datetime and date fields causes infinite loop in pydantic
IDs: CVE-2021-29510, GHSA-5jqp-qgf6-3pvh
Record: https://patchnext.com/advisories/cve-2021-29510 (revision 3, source checked 26 Oct 2026, 13:45 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: pydantic 1.8.2, 1.7.4, 1.6.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI pydantic: affected < 1.6.2; >= 1.8, < 1.8.2; >= 1.7, < 1.7.4; fixed in 1.7.4, 1.8.2, 1.6.2

## Suggested inspection (read-only)
- `python -m pip show pydantic`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on pydantic.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-5jqp-qgf6-3pvh (OSV record GHSA-5jqp-qgf6-3pvh lists affected ranges: PyPI pydantic >=0 =1.8 =1.7 <1.7.4 (fixed))
- Verified: https://github.com/advisories/GHSA-5jqp-qgf6-3pvh (GitHub-reviewed advisory GHSA-5jqp-qgf6-3pvh lists affected ranges: PyPI pydantic >=0 =1.8 =1.7 <1.7.4)

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