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CVE-2026-33191

Free5gc Udm vulnerability

8.6 HIGHEPSS 0.58%
  1. Published20 Mar 2026

Description

Free5GC is an open-source Linux Foundation project for 5th generation (5G) mobile core networks. Versions prior to 1.4.2 are vulnerable to null byte injection in URL path parameters. A remote attacker can inject null bytes (URL-encoded as %00) into the supi path parameter of the UDM's Nudm_SubscriberDataManagement API. This causes URL parsing failure in Go's net/url package with the error "invalid control character in URL", resulting in a 500 Internal Server Error. This null byte injection vulnerability can be exploited for denial of service attacks. When the supi parameter contains null characters, the UDM attempts to construct a URL for UDR that includes these control characters. Go's URL parser rejects them, causing the request to fail with 500 instead of properly validating input and returning 400 Bad Request. This issue has been fixed in version 1.4.2.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeChanged
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Affected products

Free5gc Udm< 1.4.2

Remediation

Fixed in
Free5gc Udm≥ 1.4.2

References

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Frequently asked

Is CVE-2026-33191 being actively exploited?

CVE-2026-33191 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.58%.

How severe is CVE-2026-33191?

CVE-2026-33191 has a CVSS 3.1 base score of 8.6, rated high. EPSS estimates a 0.58% probability of exploitation.

Which products are affected by CVE-2026-33191?

Affected products include Free5gc Udm.

How do I fix CVE-2026-33191?

Upgrade affected software to a fixed version, for example Free5gc Udm 1.4.2 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-33191 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.