CVE-2026-41135: free5GC PCF: Memory Leak via CORS Middleware Registration in HTTP Handler Leads to Denial of Service

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-04-22 · updated 2026-10-26
Weakness: CWE-400

Description

free5GC UDR is the Policy Control Function (PCF) for free5GC, an an open-source project for 5th generation (5G) mobile core networks. A memory leak vulnerability in versions prior to 1.4.3 allows any unauthenticated attacker with network access to the PCF SBI interface to cause uncontrolled memory growth by sending repeated HTTP requests to the OAM endpoint. The root cause is a `router.Use()` call inside an HTTP handler that registers a new CORS middleware on every incoming request, permanently growing the Gin router's handler chain. This leads to progressive memory exhaustion and eventual Denial of Service of the PCF, preventing all UEs from obtaining AM and SM policies and blocking 5G session establishment. Version 1.4.3 contains a patch.

Affected products

free5gc: through 4.2.1
Free5GC pcf: before 1.4.3 — fixed in 1.4.3

How to fix

Upgrade to a fixed version: Free5GC pcf 1.4.3. Check the vendor advisory for mitigations.

References

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