CVE-2026-33534
MediumPublic exploitEspoCRM has authenticated SSRF via internal-host validation bypass using alternative IPv4 notation
Published Apr 13, 2026 · Updated Aug 12, 2026 · Also known as GHSA-h7gx-8gwv-7g73
Key Facts
Routine patching- CVE-2026-33534 is a medium-severity vulnerability (CVSS 4.3 v3.1) affecting Espocrm.
- It is not listed in any known-exploited vulnerabilities catalog. Public exploit code is available.
- EPSS estimates a 1.7% probability of exploitation in the next 30 days.
- Fixed versions are available, including Espocrm 9.3.4.
- Brandefense priority: routine patching, as no exploitation is known and its severity is moderate or low.
CVSS v3.1
4.3
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
EPSS (30-day exploit likelihood)
1.7%
Higher than 76.6% of all scored CVEs
Exploited in the wild
No known
Not in a known-exploited catalog
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2026-33534 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
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.
Affected Products
2 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| EspocrmEspocrm | >= < 9.3.4 | 9.3.4 |
Patched Releases
Espocrm
9.3.4
Timeline
Publicly disclosed
Apr 13, 2026
Last updated
Aug 12, 2026
Weakness Type
- CWE-918 Server-Side Request Forgery (SSRF)
References
- advisoryhttps://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33534.json
- advisoryhttps://nvd.nist.gov/vuln/detail/CVE-2026-33534
- exploitExploitDB-52583
- otherhttps://github.com/espocrm/espocrm/releases/tag/9.3.4
- otherhttps://github.com/espocrm/espocrm/security/advisories/GHSA-h7gx-8gwv-7g73
FAQ
Common Questions.
EspoCRM is an open source customer relationship management application.
Affected: Espocrm versions >= < 9.3.4. The full list is in the CVE brief.
It is not listed in any known-exploited vulnerabilities catalog.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
Public exploit code is available.
Fixed versions are available, including Espocrm 9.3.4.
Brandefense priority: routine patching, as no exploitation is known and its severity is moderate or low.
Is CVE-2026-33534 Running On Your Attack Surface?
Brandefense maps vulnerabilities like this one to your internet-facing assets and tells you exactly where to patch.
Request A Demo