Django EmailBackend cleartext read via failed STARTTLS before 6.0.6/5.2.15
CVE-2026-7666 Published on June 3, 2026
Potential unencrypted email transmission via STARTTLS in the SMTP backend
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.
Timeline
Initial report received.
Vulnerability confirmed. 20 days later.
Security release issued. 22 days later.
Weakness Type
Cleartext Transmission of Sensitive Information
The software transmits sensitive or security-critical data in cleartext in a communication channel that can be sniffed by unauthorized actors. Many communication channels can be "sniffed" by attackers during data transmission. For example, network traffic can often be sniffed by any attacker who has access to a network interface. This significantly lowers the difficulty of exploitation by attackers.
Products Associated with CVE-2026-7666
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Affected Versions
djangoproject Django:- Version 6.0 and below 6.0.6 is affected.
- Version 6.0.6 is unaffected.
- Version 5.2 and below 5.2.15 is affected.
- Version 5.2.15 is unaffected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.