CVE-2026-33534: EspoCRM is an open source customer relationship management application. Versions 9.3.3 and below have an authenticated Server-Side Request Forgery (SS...

Description

EspoCRM is an open source customer relationship management application. Versions 9.3.3 and below have an authenticated Server-Side Request Forgery (SSRF) vulnerability that allows bypassing the internal-host validation logic by using alternative IPv4 representations such as octal notation (e.g., 0177.0.0.1 instead of 127.0.0.1). This is caused by HostCheck::isNotInternalHost() function relying on PHP's filter_var(..., FILTER_VALIDATE_IP), which does not recognize alternative IP formats, causing the validation to fall through to a DNS lookup that returns no records and incorrectly treats the host as safe, however the cURL subsequently normalizes the address and connects to the loopback destination. Through the confirmed /api/v1/Attachment/fromImageUrl endpoint, an authenticated user can force the server to make requests to loopback-only services and store the fetched response as an attachment. This vulnerability is distinct from CVE-2023-46736 (which involved redirect-based SSRF) and may allow access to internal resources reachable from the application runtime. This issue has been fixed in version 9.3.4.

Metrics

CVSS 3.1

4.3/10

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

EPSS Probability

1.98%

78.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-918

Affected Software

Vendor	Product	Versions
Espocrm	Espocrm	< 9.3.4

References

https://github.com/espocrm/espocrm/releases/tag/9.3.4Release Notes
https://github.com/espocrm/espocrm/security/advisories/GHSA-h7gx-8gwv-7g73Exploit, Vendor Advisory
https://github.com/espocrm/espocrm/security/advisories/GHSA-h7gx-8gwv-7g73Exploit, Vendor Advisory

Timeline

Published: Apr 13, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-33534?

EspoCRM is an open source customer relationship management application. Versions 9.3.3 and below have an authenticated Server-Side Request Forgery (SSRF) vulnerability that allows bypassing the internal-host validation logic by using alternative IPv4 representations such as octal notation (e.g., 0177.0.0.1 instead of 127.0.0.1). This is caused by HostCheck::isNotInternalHost() function relying on PHP's filter_var(..., FILTER_VALIDATE_IP), which does not recognize alternative IP formats, causing the validation to fall through to a DNS lookup that returns no records and incorrectly treats the host as safe, however the cURL subsequently normalizes the address and connects to the loopback destination. Through the confirmed /api/v1/Attachment/fromImageUrl endpoint, an authenticated user can force the server to make requests to loopback-only services and store the fetched response as an attachment. This vulnerability is distinct from CVE-2023-46736 (which involved redirect-based SSRF) and may allow access to internal resources reachable from the application runtime. This issue has been fixed in version 9.3.4.

How severe is CVE-2026-33534?

CVE-2026-33534 has a CVSS score of 4.3/10 (MEDIUM severity). The EPSS model estimates a 1.98% probability of exploitation in the next 30 days.

How do I fix CVE-2026-33534?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.