Authenticated SMTP Sender Address Forgery

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-33586
StatePUBLISHED
AssignerENISA
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-07 16:17:47 UTC
Updated2026-10-08 21:33:42 UTC
DescriptionAuthenticated 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.

Risk And Classification

Primary CVSS: v4.0 6.3 MEDIUM from a6d3dc9e-0591-4a13-bce7-0f5b31ff6158

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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS: 0.001390000 probability, percentile 0.028430000 (date 2026-10-10)

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

VersionSourceTypeScoreSeverityVector
4.0a6d3dc9e-0591-4a13-bce7-0f5b31ff6158Secondary6.3MEDIUMCVSS: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/C...
4.0CNACVSS6.3MEDIUMCVSS: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

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
Low
User Interaction
None
Confidentiality
None
Integrity
None
Availability
None
Sub Conf.
None
Sub Integrity
High
Sub Availability
None

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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA OVHcloud OVHcloud affected 2026-07-20 date Not specified

References

ReferenceSourceLinkTags
docs.ovhcloud.com/en/guides/web-cloud/email-and-collaborative-solutions/trouble... a6d3dc9e-0591-4a13-bce7-0f5b31ff6158 docs.ovhcloud.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Abdullah HAMED of ENGIE IT Offensive Cybersecurity Team (en)

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