CVE-2026-40343: free5GC UDR Fail-open Handling Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-jwch-w7wh-gqjm",
  "modified" : "2026-04-24T21:11:11Z",
  "published" : "2026-04-21T19:05:18Z",
  "aliases" : [ "CVE-2026-40343" ],
  "summary" : "free5GC UDR: Fail-open handling in PolicyDataSubsToNotifyPost allows unintended subscription creation",
  "details" : "### Summary\nA fail-open request handling flaw in the UDR service causes the `/nudr-dr/v2/policy-data/subs-to-notify` POST handler to continue processing requests even after request body retrieval or deserialization errors.\n\nThis may allow unintended creation of Policy Data notification subscriptions with invalid, empty, or partially processed input, depending on downstream processor behavior.\n\n### Details\nThe endpoint `POST /nudr-dr/v2/policy-data/subs-to-notify` is intended to create a Policy Data notification subscription only after the HTTP request body has been successfully read and parsed into a valid `PolicyDataSubscription` object. [file:93]\n\nIn the free5GC UDR implementation, the function `HandlePolicyDataSubsToNotifyPost` in `NFs/udr/internal/sbi/api_datarepository.go` does not terminate execution after input-processing failures. [file:93]\n\nThe request flow is:\n\n1. The handler calls `c.GetRawData()` to read the HTTP request body. [file:93]\n2. If `GetRawData()` fails, the handler sends an HTTP 500 error response, but **does not return**. [file:93]\n3. The handler then calls `openapi.Deserialize(policyDataSubscription, reqBody, \"application/json\")`. [file:93]\n4. If deserialization fails, the handler sends an HTTP 400 error response, but again **does not return**. [file:93]\n5. Execution continues and the handler still invokes `s.Processor().PolicyDataSubsToNotifyPostProcedure(c,policyDataSubscription)`. [file:93]\n\nAs a result, the endpoint operates in a fail-open manner: request processing may continue after fatal input validation or body handling errors, instead of being safely aborted. [file:93]\n\nThis differs from safer handlers in the same file, which use a helper pattern that explicitly returns on body read or deserialization failure before calling the corresponding processor routine. [file:93]\n\n### Security Impact\nThis issue affects a write-capable API that creates Policy Data notification subscriptions. [file:93]  \nBecause execution continues after body read or parsing failure, the processor may receive an uninitialized, partially initialized, or otherwise unintended `PolicyDataSubscription` object. [file:93]\n\nThe exact runtime impact depends on downstream processor behavior and storage validation. [file:93]  \nAt minimum, this is a security-relevant robustness flaw that can lead to inconsistent request handling; under certain runtime conditions it may allow creation of invalid or unintended subscription state. [file:93]\n\n### Reproduction Status\nThe code path has been statically confirmed. [file:93]  A complete runtime proof of unintended subscription creation after `GetRawData()` or deserialization failure has not yet been established. [file:93]\n\n### Patch\nThe handler should immediately terminate after sending an error response for body read or deserialization failure. [file:93]\n\nA minimal fix is to add missing `return` statements in `HandlePolicyDataSubsToNotifyPost`:\n\n```go\nreqBody, err := c.GetRawData()\nif err != nil {\n    logger.DataRepoLog.Errorf(\"Get Request Body error: %+v\", err)\n    pd := openapi.ProblemDetailsSystemFailure(err.Error())\n    c.Set(sbi.IN_PB_DETAILS_CTX_STR, pd.Cause)\n    c.JSON(http.StatusInternalServerError, pd)\n    return\n}\n\nerr = openapi.Deserialize(&policyDataSubscription, reqBody, \"application/json\")\nif err != nil {\n    logger.DataRepoLog.Errorf(\"Deserialize Request Body error: %+v\", err)\n    pd := util.ProblemDetailsMalformedReqSyntax(err.Error())\n    c.Set(sbi.IN_PB_DETAILS_CTX_STR, pd.Cause)\n    c.JSON(http.StatusBadRequest, pd)\n    return\n}\n```\nAdditionally, the deserialization call should pass a pointer to the destination\nobject so that the parsed body is written into the intended structure. [file:93]\n\n###Details\nThe issue is compounded by the handler's deserialization call, which passes\n`policyDataSubscription` directly to `openapi.Deserialize(...)` instead of\npassing a pointer to the destination object. This inconsistent usage further\nincreases the risk that request processing continues with an empty, partially\ninitialized, or otherwise unintended subscription object. [file:93]",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/free5gc/udr"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "1.4.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/free5gc/free5gc/security/advisories/GHSA-jwch-w7wh-gqjm"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-40343"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/free5gc/free5gc"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-754" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-21T19:05:18Z",
    "nvd_published_at" : "2026-04-22T00:16:27Z"
  }
}