CVE-2026-33586
Authenticated SMTP Sender Address Forgery
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.
INFO
Published Date :
Oct. 7, 2026, 4:17 p.m.
Last Modified :
Oct. 7, 2026, 4:17 p.m.
Remotely Exploit :
Yes !
Source :
a6d3dc9e-0591-4a13-bce7-0f5b31ff6158
Affected Products
The following products are affected by CVE-2026-33586
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 4.0 | MEDIUM | a6d3dc9e-0591-4a13-bce7-0f5b31ff6158 | ||||
| CVSS 4.0 | MEDIUM | a6d3dc9e-0591-4a13-bce7-0f5b31ff6158 |
Solution
- Update SPF records to include specific authorized sending IPs.
- Disable email sending for unauthorized users.
- Implement stricter sender validation checks.
- Monitor mail logs for suspicious activity.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-33586.
| URL | Resource |
|---|---|
| https://docs.ovhcloud.com/en/guides/web-cloud/email-and-collaborative-solutions/troubleshooting/email-rejected-cross-domain-spoofing |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-33586 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-33586
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-33586 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-33586 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by a6d3dc9e-0591-4a13-bce7-0f5b31ff6158
Oct. 07, 2026
Action Type Old Value New Value Added 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. Added CVSS V4.0 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 Added CWE CWE-346 Added CWE CWE-1188 Added CWE CWE-290 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/33xxx/CVE-2026-33586.json">CVE-2026-33586</a> Added Reference https://docs.ovhcloud.com/en/guides/web-cloud/email-and-collaborative-solutions/troubleshooting/email-rejected-cross-domain-spoofing