Medium exploit reference

CVE-2026-33657 — EspoCRM: Stored HTML injection in email notifications about stream notes via unescaped post field

EspoCRM 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.

Published Apr 13, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: GitHub_M

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.2% (30-day exploitation probability)+2
Technical severity (medium)+3
CISA SSVC: exploitation "poc"+5

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.25%

ahead of 15% of scored CVEs · Oct 14, 2026

Affects

Espocrm

CVSS base

5.4

Medium · 3 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

Proof of concept

none · proof-of-concept · active

Automatable

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Espocrm Espocrm).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Exploitation requires user interaction: tighten email/web filtering and warn affected users.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Espocrm	Espocrm	< 9.3.4	Vulnerable	NIST National Vulnerability Database
Espocrm	Espocrm	version < 9.3.4	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

Low

User interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
5.4	CVSS 3.1	Medium	2.3	2.7	nvd@nist.gov via NIST National Vulnerability Database
4.6	CVSS 3.1	Medium	2.1	2.5	security-advisories@github.com via NIST National Vulnerability Database
4.6	CVSS 3.1	Medium	—	—	GitHub_M via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N (score shown at the top: nvd@nist.gov)

Scoring entities (NIST, CNA, ADP) score independently; each score is shown with its origin. For prioritization we use 5.4 (NVD (NIST)) as a conservative provisional reference — not a definitive official score.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-80

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.25%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).

web/proxy/WAF logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first.

2026
Affected products added · espocrm/espocrm
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
CVSS changed · 5.4
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Analyzed
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
Apr 13, 2026 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

2 on the record

github.com/espocrm/espocrm/security/advisories/GHSA-8prm-r5j9-j574
Exploit, Vendor Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
github.com/espocrm/espocrm/releases/tag/9.3.4
Release Notes, x_refsource_MISC, NIST National Vulnerability Database

Elsewhere on this site

Espocrm
every CVE for this vendor

CWE-80
other pages naming this weakness

Related CVEs (same products)

Medium CVE-2026-75505 EspoCRM: Access control bypass in Mass Update letting regular user with Mass Update permission read any attachment 3h
Medium CVE-2026-77460 EspoCRM: Mass email template renderer leaks restricted record fields 4h
Medium CVE-2026-59994 EspoCRM: Pre-authentication stored HTML injection in stream notification emails about email received 4h
Medium CVE-2026-63130 EspoCRM: Admin path traversal in LabelManager (Custom Label saving) allows arbitrary `.json` file read, write and delete 4h
Low CVE-2026-53575 EspoCRM: Persistent XSS via CSP nonce injection in applicationName setting by admin user 4h
High CVE-2026-53574 EspoCRM: Blind SQL injection via streamAttachments where-clause complex expression 4h

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-33657 is "EspoCRM: Stored HTML injection in email notifications about stream notes via unescaped post field", rated Medium. It affects Espocrm (Espocrm); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.4 describes technical severity. EPSS 0.25% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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