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Medium, CVSS 5.3amended

PyMongo: PYTHON-5990 Forced Unix domain socket connection via a .sock KMS endpoint in client-side field level encryption

CVE-2026-96747GHSA-qx36-8mw2-4r3x

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (pymongo 4.18.2), 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 pymongo

    Affected
    >= 3.9.0, <= 4.18.1
    Fixed in
    4.18.2

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:L/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N · score source
EPSS
  • CVE-2026-96747: 0.19% estimated exploitation activity in the next 30 days; percentile 8.70 (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.

Summary PyMongo passed the KMS endpoint of a data key verbatim into parsehost(), which returns any string ending in .sock unchanged instead of validating it as a hostname and port. The driver's connection code then treats such an address as a Unix domain socket path and connects to it with AFUNIX. Because the endpoint originates from masterKey.endpoint in a key vault document, a party who can write to the key vault could redirect the driver's KMS connection to an arbitrary Unix domain socket path on the application host. Impact An application using client-side field level encryption (CSFLE) or Queryable Encryption is affected if an attacker can write to its key vault collection. Setting masterKey.endpoint on a data key to a .sock-suffixed string causes the next KMS request for that key (key cache TTL is ~60 seconds) to open an AFUNIX connection to the attacker-chosen filesystem path from inside the victim application process. The documented custom KMS endpoint feature supports TCP…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 4 · amended ·

    Amended from ghsa record GHSA-qx36-8mw2-4r3x

  2. Revision 3 · amended ·

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

  3. Revision 2 · amended ·

    Amended from osv record GHSA-qx36-8mw2-4r3x

  4. Revision 1 · created ·

    Published from ghsa record GHSA-qx36-8mw2-4r3x

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-96747

Advisory: PyMongo: PYTHON-5990 Forced Unix domain socket connection via a .sock KMS endpoint in client-side field level encryption
IDs: CVE-2026-96747, GHSA-qx36-8mw2-4r3x
Record: https://patchnext.com/advisories/cve-2026-96747 (revision 4, source checked 26 Oct 2026, 13:55 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: pymongo 4.18.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI pymongo: affected >= 3.9.0, <= 4.18.1; fixed in 4.18.2

## Suggested inspection (read-only)
- `python -m pip show pymongo`: 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 pymongo.
- 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://github.com/advisories/GHSA-qx36-8mw2-4r3x (GitHub-reviewed advisory GHSA-qx36-8mw2-4r3x lists affected ranges: PyPI pymongo >=3.9.0 <=4.18.1)
- Verified: https://osv.dev/vulnerability/GHSA-qx36-8mw2-4r3x (OSV record GHSA-qx36-8mw2-4r3x lists affected ranges: PyPI pymongo >=3.9.0 <4.18.2 (fixed))

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