Free5GC up to 4.2.1 UDR Service {subsId} unusual condition

Summaryinfo

A vulnerability classified as critical has been found in Free5GC up to 4.2.1. The affected element is an unknown function of the file /nudr-dr/v2/policy-data/subs-to-notify/{subsId} of the component UDR Service. This manipulation causes unusual condition. The identification of this vulnerability is CVE-2026-40249. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability has been found in Free5GC up to 4.2.1 and classified as critical. Affected by this vulnerability is some unknown processing of the file /nudr-dr/v2/policy-data/subs-to-notify/{subsId} of the component UDR Service. The manipulation with an unknown input leads to a unusual condition vulnerability. The CWE definition for the vulnerability is CWE-754. The product does not check or incorrectly checks for unusual or exceptional conditions that are not expected to occur frequently during day to day operation of the product. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

free5GC is an open-source implementation of the 5G core network. In versions 4.2.1 and below of the UDR service, the PUT handler for updating Policy Data notification subscriptions at /nudr-dr/v2/policy-data/subs-to-notify/{subsId} does not return after request body retrieval or deserialization errors. Although HTTP 500 or 400 error responses are sent, execution continues and the processor is invoked with a potentially uninitialized or partially initialized PolicyDataSubscription object. This fail-open behavior may allow unintended modification of existing Policy Data notification subscriptions with invalid or empty input, depending on downstream processor and storage behavior. A patched version was not available at the time of publication.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-40249 since 04/10/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 04/17/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Name

• Free5GC

Version

• 4.2.0
• 4.2.1

Website

• Product: https://github.com/free5gc/free5gc/

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