CVE-2026-33191Network attack vector

API request interruption via unvalidated null byte

Published Mar 20, 2026 · Updated Mar 20, 2026

Null byte injection in free5GC UDM before 1.4.2 allows remote attackers to interrupt API requests through a crafted SUPI path value. Subscriber Data Management handlers pass an unvalidated supi or ueId value into downstream UDR URL construction, where Go's net/url parser rejects the embedded control character and returns HTTP 500. No authentication or user interaction is required; a crafted %00 value can repeatedly fail affected UDM requests, but published evidence does not establish a process crash.

CVSS severity8.7
High
EPSS probability0.35%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Null byte injection in free5GC UDM before 1.4.2 allows remote attackers to interrupt API requests through a crafted SUPI path value. Subscriber Data Management handlers pass an unvalidated supi or ueId value into downstream UDR URL construction, where Go's net/url parser rejects the embedded control character and returns HTTP 500. No authentication or user interaction is required; a crafted %00 value can repeatedly fail affected UDM requests, but published evidence does not establish a process crash.

The record

CVE
CVE-2026-33191
Published
Mar 20, 2026
Updated
Mar 20, 2026
Vendor
free5GC
Product
free5GC
Classifications
CWE-248, CWE-158, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 20, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 20, 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

8.7GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
8.6NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-248Uncaught Exception
CWE-158Improper Neutralization of Null Byte or NUL Character
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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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