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

Severity: medium (CVSS 5.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 8.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-04-22 · updated 2026-10-26
Weakness: CWE-754

Description

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.

Affected products

free5gc: through 4.2.1
free5gc udr: through 1.4.2

References

https://github.com/free5gc/free5gc/security/advisories/GHSA-jwch-w7wh-gqjm

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