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CVE-2026-33659— EspoCRM: SSRF via DNS Rebinding in Attachment fromImageUrl Endpoint Allows Internal Network Access

Quick assessment

Affected
espocrm espocrm
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

EspoCRM是EspoCRM开源的一套开源的基于Web的客户关系管理系统（CRM）。该系统提供销售自动化、社区和客户支持等功能。 EspoCRM 9.3.3及之前版本存在代码问题漏洞，该漏洞源于POST /api/v1/Attachment/fromImageUrl端点存在DNS重绑定条件，可能导致服务端请求伪造攻击。

CVSS 3.5 · Low EPSS 0.40% · P32
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I. Basic Information for CVE-2026-33659

Vulnerability Information
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Vulnerability Title
EspoCRM: SSRF via DNS Rebinding in Attachment fromImageUrl Endpoint Allows Internal Network Access
Source: CVE Program / CVE List V5
Vulnerability Description
EspoCRM is an open source customer relationship management application. In versions 9.3.3 and below, the POST /api/v1/Attachment/fromImageUrl endpoint is vulnerable to Server-Side Request Forgery (SSRF) via a DNS rebinding (TOCTOU) condition. Host validation uses dns_get_record() but the actual HTTP request resolves hostnames through curl's internal resolver (gethostbyname()), allowing the two lookups to return different IP addresses for the same hostname. A secondary issue exists where an empty DNS result (due to DNS failure, IPv6-only domains, or non-existent hostnames) causes the validation to implicitly allow the host without further checks. An authenticated attacker with default attachment creation access can exploit this gap to bypass internal IP restrictions and scan internal network ports, confirm the existence of internal hosts, and interact with internal HTTP-based services, though data extraction from binary protocol services and remote code execution are not possible through this endpoint. This issue has been fixed in version 9.3.4.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
服务端请求伪造(SSRF)
Source: CVE Program / CVE List V5
Vulnerability Title
EspoCRM 代码问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
EspoCRM是EspoCRM开源的一套开源的基于Web的客户关系管理系统（CRM）。该系统提供销售自动化、社区和客户支持等功能。 EspoCRM 9.3.3及之前版本存在代码问题漏洞，该漏洞源于POST /api/v1/Attachment/fromImageUrl端点存在DNS重绑定条件，可能导致服务端请求伪造攻击。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
espocrm espocrm < 9.3.4 -

II. Public POCs for CVE-2026-33659

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III. Intelligence Information for CVE-2026-33659

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Patches & Fixes for CVE-2026-33659 (1)

Vendor Advisories for CVE-2026-33659 (1)

Same Patch Batch · espocrm · 2026-04-13 · 4 CVEs total

CVE-2026-33740 5.4 MEDIUM EspoCRM: Email importEml can import and delete another user's attachment by raw fileId
CVE-2026-33657 4.6 MEDIUM EspoCRM: Stored HTML injection in email notifications about stream notes via unescaped pos
CVE-2026-33534 4.3 MEDIUM EspoCRM has authenticated SSRF via internal-host validation bypass using alternative IPv4

IV. Related Vulnerabilities

Same product: espocrm
Same vendor: espocrm
Same weakness: CWE-918

V. Comments for CVE-2026-33659

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