Unrated

Cross-tenant sender-domain spoofing in N-able Mail Assure SMTP relay

IdentifiersCVE-2025-68624CWE-290

CVE-2025-68624 is a disputed design-level authorization flaw in N-able Mail Assure’s cloud multi-tenant SMTP relay service. According to the provided reporting, the platform authenticates SMTP users but does not enforce that the authenticated tenant is authorized to use the claimed sender domain during message submission. As a result, an authenticated SMTP user from one tenant can submit outbound email using sender addresses belonging to other unrelated tenants hosted on the same Mail Assure platform. The reported issue is not a credential bypass in the classic sense; rather, it is a missing sender-domain authorization control in a shared relay architecture. The supplied context states that when the spoofed domain already authorizes Mail Assure infrastructure in SPF and the message uses an aligned RFC5322.From domain, downstream receivers such as Microsoft 365 may accept the message with SPF PASS and DMARC PASS, including for domains with strict DMARC enforcement.

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ANALYST BRIEF

Impact, mitigation & remediation

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Impact

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Successful exploitation allows cross-tenant impersonation of unrelated customer domains hosted on the same Mail Assure platform. The reported security impact includes phishing, business email compromise, vendor impersonation, and other social-engineering attacks that benefit from messages appearing to originate from a trusted domain and potentially passing SPF and DMARC validation at the recipient side. Based on the provided context, exploitation does not inherently grant mailbox access, private user data, or platform administrative control, but it can materially increase the credibility and deliverability of spoofed email.

Mitigation

If you can’t patch tonight, do this now.

Until a platform-side fix is available, mitigation would require restricting or disabling shared-relay behavior that permits cross-tenant sender usage, and implementing explicit per-tenant sender-domain allowlists or binding authenticated SMTP accounts to approved domains only. Operators should review outbound relay policies for tenant isolation, monitor for anomalous cross-domain submissions, and consider limiting SMTP submission privileges to only necessary accounts. The provided content does not include official vendor mitigation guidance, so this mitigation guidance is inferred from the described flaw.

Remediation

Patch, then assume compromise.

The reported remediation is to enforce sender-domain authorization at SMTP submission time. Specifically, Mail Assure should verify that the authenticated SMTP identity or tenant is explicitly authorized to send using the claimed envelope sender and aligned RFC5322.From domain, and should reject submissions attempting to use domains belonging to unrelated tenants without delegated permission or administrative relationship. Because the content does not provide a vendor-issued fix, patch version, or formal remediation advisory, specific product-version remediation information is currently not available.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

ACTIVITY FEED

Recent activity

2 sources tracked across advisories and community write-ups. News coverage will land here when it surfaces.

2 SOURCESView more in app

No news coverage yet. Advisories and community discussion only.

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Threat actor evidence

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Associated malware

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Detection signatures

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Vendor-by-vendor mapping

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