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CVE-2026-33586— Authenticated SMTP Sender Address Forgery

Quick assessment

Affected
OVHcloud OVHcloud
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

已认证用户可以通过 OVH 邮件服务器在发送邮件时，同时操控 SMTP 信封中的“Envelope-from”字段和邮件头中的“From”字段。 由于 OVH 的默认 SPF（发件人策略框架）配置通常包含 机制，任何拥有有效 OVH 电子邮件账户的已认证用户，都可以借助默认的 SPF 记录，发送看似源自任何 OVH 托管域的邮件。鉴于 SPF 策略明确授权 OVH 邮件服务器（mx.ovh.com）代这些域发送邮件，即使发送方并未获得被伪造域名所有者的授权，这些伪造邮件仍能成功通过 SPF 验证。

CVSS 6.3 · Medium

Possible ATT&CK Techniques 1 AI

T1571.001

Affected Version Matrix 1

VendorProduct Version RangeStatus
OVHcloud OVHcloud < 2026-07-20 affected
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I. Basic Information for CVE-2026-33586

Vulnerability Information
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Vulnerability Title
Authenticated SMTP Sender Address Forgery
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
不安全的默认资源初始化
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
OVHcloud OVHcloud 0 ~ 2026-07-20 -

II. Public POCs for CVE-2026-33586

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III. Intelligence Information for CVE-2026-33586

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Vendor Pages for CVE-2026-33586 (1)

IV. Related Vulnerabilities

Same weakness: CWE-1188

V. Comments for CVE-2026-33586

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