CVE-2026-33659
EspoCRM: SSRF via DNS Rebinding in Attachment fromImageUrl Endpoint Allows Internal Network Access
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.
INFO
Published Date :
April 13, 2026, 9:16 p.m.
Last Modified :
April 13, 2026, 9:16 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-33659
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | LOW | [email protected] |
Solution
- Update EspoCRM to version 9.3.4 or higher.
- Ensure host validation is robust.
- Implement strict network segmentation.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-33659.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-33659 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-33659
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
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The following list is the news that have been mention
CVE-2026-33659 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-33659 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Apr. 13, 2026
Action Type Old Value New Value Added 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. Added CVSS V3.1 AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:N/A:N Added CWE CWE-918 Added CWE CWE-367 Added Reference https://github.com/espocrm/espocrm/commit/dca03cc3458e487362c26c746378a2d4de9990b1 Added Reference https://github.com/espocrm/espocrm/releases/tag/9.3.4 Added Reference https://github.com/espocrm/espocrm/security/advisories/GHSA-6m4j-fwrx-crh7