CVE-2026-40343: free5GC UDR: Fail-open handling in PolicyDataSubsToNotifyPost allows unintended subscription creation

CVE-2026-40343 · Severity: medium · CVSS 5.8 · Published 2026-04-22

free5GC UDR is the user data repository (UDR) for free5GC, an an open-source project for 5th generation (5G) mobile core networks. In versions up to and including 1.4.2, a 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. This may allow unintended creation of Policy Data notification subscriptions with invalid, empty, or partially processed input, depending on downstream processor behavior. As of time of publication, a patched version is not available.

Technologies: free5GC, free5GC Udr, github.com/free5gc/udr (Go). Vendors: free5GC, Go.

Quick answers

Is CVE-2026-40343 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-40343 being exploited in the wild.
How severe is CVE-2026-40343?
Medium severity, with a CVSS score of 5.8, published 22 April 2026.
Which products and versions are affected?
github.com/free5gc/udr (Go) <= 1.4.2, SEMVER:introduced=0, SEMVER:introduced=0,last_affected=1.4.2.
Is there a fix for CVE-2026-40343?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
Am I affected by CVE-2026-40343?
Check whether you run free5GC, free5GC Udr or github.com/free5gc/udr (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Affected products

  • free5GC
  • free5GC Udr
  • github.com/free5gc/udr (Go) <= 1.4.2, SEMVER:introduced=0, SEMVER:introduced=0,last_affected=1.4.2

Identifiers

  • CVE-2026-40343
  • GHSA-jwch-w7wh-gqjm
  • GO-2026-5482

References

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