EspoCRM: Stored HTML injection in email notifications about stream notes via unescaped post field

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Summary

CVECVE-2026-33657
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-13 20:16:34 UTC
Updated2026-04-13 21:16:24 UTC
DescriptionEspoCRM is an open source customer relationship management application. Versions 9.3.3 and below have a stored HTML injection vulnerability that allows any authenticated user with standard (non-administrative) privileges to inject arbitrary HTML into system-generated email notifications by crafting malicious content in the post field of stream activity notes. The vulnerability exists because server-side Handlebars templates render the post field using unescaped triple-brace syntax, the Markdown processor preserves inline HTML by default, and the rendering pipeline explicitly skips sanitization for fields present in additionalData, creating a path where attacker-controlled HTML is accepted, stored, and rendered directly into emails without any escaping. Since the emails are sent using the system's configured SMTP identity (such as an administrative sender address), the injected content appears fully trusted to recipients, enabling phishing attacks, user tracking via embedded resources like image beacons, and UI manipulation within email content. The @mention feature further increases the impact by allowing targeted delivery of malicious emails to specific users. This issue has been fixed in version 9.3.4.

Risk And Classification

Primary CVSS: v3.1 4.6 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N

Problem Types: CWE-80 | CWE-116 | CWE-80 CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS) | CWE-116 CWE-116: Improper Encoding or Escaping of Output

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary4.6MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N
3.1CNADECLARED4.6MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
Required
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Espocrm Espocrm affected < 9.3.4 Not specified

References

ReferenceSourceLinkTags
github.com/espocrm/espocrm/security/advisories/GHSA-8prm-r5j9-j574 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
github.com/espocrm/espocrm/releases/tag/9.3.4 [email protected] github.com
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