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

Severity: low (CVSS 3.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-04-13 · updated 2026-06-17
Weakness: CWE-367

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.

Affected products

espocrm: before 9.3.4 — fixed in 9.3.4

How to fix

Upgrade to a fixed version: espocrm 9.3.4. Check the vendor advisory for mitigations.

References

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