CVE-2026-7666: Django Django Fails To Prevent Reuse Vulnerability

LOW
Advisory Identifier: GHSA-mm6v-q8q9-pgcf
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CVSS 3.1
CWE-319
Published
Advisory Summary

CVE-2026-7666 is a LOW (CVSS 3.1) django fails to prevent reuse vulnerability (CWE-319: Cleartext Transmission of Sensitive Information) affecting Django libraries in the PyPI ecosystem. The issue involves django fails to prevent reuse of a partially-initialized connection after a failed `starttls` handshake. Remediation is available by upgrading affected packages to version 5.2.15, 6.0.6.

CVE-2026-7666 at a Glance

CVE Identifier CVE-2026-7666
GHSA Identifier GHSA-mm6v-q8q9-pgcf
Severity LOW
CVSS v3.1 Base Score 3.1
CWE Classification CWE-319: Cleartext Transmission of Sensitive Information
Affected Product Django
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 3.1

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

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

How to Fix CVE-2026-7666

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

django fixed: 5.2.15 
pip install django>=5.2.15
django fixed: 6.0.6 
pip install django>=6.0.6
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 django

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-7666, inspect your installed packages using pip:

pip show django

Analyze the terminal output to locate any version of Django in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 5.2.15), your application is affected.

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

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-319: Cleartext Transmission of Sensitive Information, where the product transmits sensitive or security-critical data in cleartext in a communication channel that can be sniffed by unauthorized actors. In Django, 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

An issue was discovered in Django 6.0 before 6.0.6 and 5.2 before 5.2.15. `django.core.mail.backends.smtp.EmailBackend` in Django fails to prevent reuse of a partially-initialized connection after a failed `STARTTLS` handshake when `fail_silently=True`, which allows on-path network attackers to read email content via cleartext interception. Earlier, unsupported Django series (such as 5.0.x, 4.1.x, and 3.2.x) were not evaluated and may also be affected. Django would like to thank Kasper Dupont for reporting this issue.

CVE-2026-7666 Affected Django Versions

2 component(s)
Fixed Versions:
5.2.156.0.6
Product / Package Ecosystem Affected Versions Fixed Version
django
pypi/django
PyPI
≥ 5.2
< 5.2.15
5.2.15
django
pypi/django
PyPI
≥ 6.0
< 6.0.6
6.0.6

References

NVD — CVE-2026-7666 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-7666
Django Release RELEASE
https://docs.djangoproject.com/en/dev/releases/security
Django Source Repository REPOSITORY
https://github.com/django/django
Django Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/django/PYSEC-2026-200.yaml
groups.google.com/g/django-announce WEB
https://groups.google.com/g/django-announce
Django Release RELEASE
https://www.djangoproject.com/weblog/2026/jun/03/security-releases

Frequently Asked Questions

What is CVE-2026-7666?
CVE-2026-7666 is a security vulnerability in Django involving Django fails to prevent reuse of a partially-initialized connection after a failed `STARTTLS` handshake under CWE-319: Cleartext Transmission of Sensitive Information.
Which Django versions are affected?
Affected versions include releases prior to 5.2.15, 6.0.6 across affected packages: django.
What version fixes CVE-2026-7666?
Upgrading to 5.2.15, 6.0.6 (or the latest patched release for your respective branch) resolves the vulnerability.
Is django affected?
Yes, django is affected in releases prior to 5.2.15, 6.0.6. Upgrade your dependency to 5.2.15, 6.0.6 or later.
What is the CVSS score of CVE-2026-7666?
CVE-2026-7666 has a CVSS v3.1 base score of 3.1 (LOW) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:N.
What CWE is associated with CVE-2026-7666?
CVE-2026-7666 is classified under CWE-319: Cleartext Transmission of Sensitive Information (The product transmits sensitive or security-critical data in cleartext in a communication channel that can be sniffed by unauthorized actors.).
How can I check PyPI dependencies for CVE-2026-7666?
Run the dependency tree command: 'pip show django'. 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-mm6v-q8q9-pgcf",
  "modified" : "2026-07-13T17:26:39Z",
  "published" : "2026-06-03T15:30:43Z",
  "aliases" : [ "CVE-2026-7666" ],
  "summary" : "Django fails to prevent reuse of a partially-initialized connection after a failed `STARTTLS` handshake",
  "details" : "An issue was discovered in Django 6.0 before 6.0.6 and 5.2 before 5.2.15.\n\n`django.core.mail.backends.smtp.EmailBackend` in Django fails to prevent reuse of a partially-initialized connection after a failed `STARTTLS` handshake when `fail_silently=True`, which allows on-path network attackers to read email content via cleartext interception.\n\nEarlier, unsupported Django series (such as 5.0.x, 4.1.x, and 3.2.x) were not evaluated and may also be affected.\nDjango would like to thank Kasper Dupont for reporting this issue.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "django"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "5.2"
      }, {
        "fixed" : "5.2.15"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "django"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "6.0"
      }, {
        "fixed" : "6.0.6"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-7666"
  }, {
    "type" : "WEB",
    "url" : "https://docs.djangoproject.com/en/dev/releases/security"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/django/django"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/django/PYSEC-2026-200.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://groups.google.com/g/django-announce"
  }, {
    "type" : "WEB",
    "url" : "https://www.djangoproject.com/weblog/2026/jun/03/security-releases"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-319" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-13T17:26:39Z",
    "nvd_published_at" : "2026-06-03T14:16:47Z"
  }
}