CVE-2026-33534 (GCVE-0-2026-33534)
Vulnerability from cvelistv5 – Published: 2026-04-13 19:20 – Updated: 2026-04-14 16:28
VLAI
EPSS
VEX
Title
EspoCRM has authenticated SSRF via internal-host validation bypass using alternative IPv4 notation
Summary
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.
Severity
4.3 (Medium)
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-04-14 15:28 UTC
CWE
- CWE-918 - Server-Side Request Forgery (SSRF)
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/espocrm/espocrm/security/advis… | x_refsource_CONFIRM |
| https://github.com/espocrm/espocrm/releases/tag/9.3.4 | x_refsource_MISC |
Impacted products
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Sightings
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|---|
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The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
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