Out-of-Bounds Slice Access in free5GC CHF Leading to DoS

Impact

This is an out-of-bounds slice access vulnerability in the CHF nchf-convergedcharging service. A valid authenticated request to PUT /nchf-convergedcharging/v3/recharging/:ueId?ratingGroup=... can trigger a server-side panic in github.com/free5gc/chf/internal/sbi.(*Server).RechargePut(...) due to an out-of-range slice access. In the reported runtime, Gin recovery converts the panic into HTTP 500, but the recharge path remains remotely panic-triggerable and can be abused repeatedly to degrade recharge functionality and flood logs. In deployments without equivalent recovery handling, this panic may cause more severe service disruption.

Patches

https://github.com/free5gc/chf/pull/61

Workarounds

• Restrict access to the nchf-convergedcharging recharge endpoint to strictly trusted NF callers only.
• Apply rate limiting or network ACLs in front of the CHF SBI interface to reduce repeated panic-trigger attempts.
• If the recharge API is not required, temporarily disable or block external reachability to this route.
• Ensure panic recovery, monitoring, and alerting are enabled.