Email Protection
CVE-2023-5770: HTML injection in email body through email subject
Proofpoint Enterprise Protection contains a vulnerability in the email delivery agent that allows an unauthenticated attacker to inject improperly encoded HTML into the email body of a message through the email subject.
Published
Automatic summary from the vendor's CVE record. We haven't written a full analysis of this vulnerability yet.
Affected and fixed versions
| Product / branch | Fixed in |
|---|---|
| Proofpoint Enterprise Protection 8.20 | patch 4809 or later |
| Proofpoint Enterprise Protection 8.20 | patch 4805 or later |
| Proofpoint Enterprise Protection 8.18 | patch 4804 or later |
| Proofpoint Enterprise Protection 8.0 | 8.18.6 or later |
Always confirm against the vendor advisory, which lists every fixed hotfix.
What it is
Proofpoint Enterprise Protection contains a vulnerability in the email delivery agent that allows an unauthenticated attacker to inject improperly encoded HTML into the email body of a message through the email subject. The vulnerability is caused by inappropriate encoding when rewriting the email before delivery.This issue affects Proofpoint Enterprise Protection: from 8.20.2 before patch 4809, from 8.20.0 before patch 4805, from 8.18.6 before patch 4804 and all other prior versions.
Sources
KEV status, EPSS score and vendor data refreshed automatically, last on 11 Oct 2026.