CVE-2026-33586

Authenticated SMTP Sender Address Forgery

State: Published
Severity: 6.3 Medium
Published: Oct 7, 2026
Updated: Oct 7, 2026
Reserved: Mar 23, 2026

Description

Authenticated users are able to manipulate both the SMTP envelope “Envelope-from” and “From” fields when sending emails through OVH mail servers.

Due to OVH's default SPF configuration, which commonly includes include:mx.ovh.com, any authenticated user with a valid OVH email account can send messages that appear to originate from any OVH-hosted domains using the default SPF record. Since the SPF policy explicitly authorizes OVH mail servers (mx.ovh.com) to send mail on behalf of these domains, forged messages successfully pass SPF validation despite not being authorized by the impersonated domain owner.

Scores

CVSS	Score	Vector	Source
4.0	6.3 Medium	CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:N/SI:H/SA:N/E:A	ENISA

Weaknesses

CWE-1188 Initialization of a resource with an insecure default
CWE-346 Origin Validation Error
CWE-290 Authentication bypass by spoofing

Affected Products

Product	Versions
OVHcloudOVHcloud	before 2026-07-20Affected

References

https://docs.ovhcloud.com/en/guides/web-cloud/email-and-collaborative-solutions/troubleshooting/email-rejected-cross-domain-spoofing

Every record here comes from the CVE Program’s CVE List. © 1999–2026 The MITRE Corporation. CVE is a registered trademark of The MITRE Corporation. The records are reproduced under the CVE Program terms of use.