CVE-2026-40248Public exploitNetwork attack vector

Unauthorized subscription writes via fail-open path validation

Published Apr 16, 2026 · Updated Apr 16, 2026

Improper authorization in free5GC UDR 4.2.1 and earlier allows remote attackers to overwrite Traffic Influence Subscriptions via SBI. The HandleApplicationDataInfluenceDataSubsToNotifySubscriptionIdPut handler sends a 404 for an invalid influenceId but continues parsing the body and writes the chosen subscriptionId. Access to the 5G Service Based Interface is required; successful requests inject attacker-controlled SUPIs and notificationUri values while returning a misleading 404.

CVSS severity8.7
High
EPSS probability0.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper authorization in free5GC UDR 4.2.1 and earlier allows remote attackers to overwrite Traffic Influence Subscriptions via SBI. The HandleApplicationDataInfluenceDataSubsToNotifySubscriptionIdPut handler sends a 404 for an invalid influenceId but continues parsing the body and writes the chosen subscriptionId. Access to the 5G Service Based Interface is required; successful requests inject attacker-controlled SUPIs and notificationUri values while returning a misleading 404.

The record

CVE
CVE-2026-40248
Published
Apr 16, 2026
Updated
Apr 16, 2026
Vendor
free5GC
Product
free5GC
Classifications
CWE-285, CWE-636, T1210
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 16, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 16, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=<= 1.4.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

free5GC · free5GCversion=<= 1.4.2

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
8.7GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-285Improper Authorization
CWE-636Not Failing Securely ('Failing Open')
T1210Exploitation of Remote Services

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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