CVE-2026-33534
EspoCRM has authenticated SSRF via internal-host validation bypass using alternative IPv4 notation
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.
- Affected
- espocrm
- CVSS v3.1 GITHUB
- 4.3 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N - EPSS
- 1.68% chance of exploitation in the next 30 days, 77th percentile
- Nuclei
- medium · CWE-918
- Published
- 2026-04-13
- Updated
- 2026-04-14
Proof-of-concept exploits (1)
- EntroVyx/CVE-2026-335340★ · 2026-10-05