CVE-2026-42459: free5gc Input Validation Flaw — Exploit

Description

free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, the free5GC UDM component fails to validate the supi path parameter in six GET handlers of the nudm-sdm (Subscriber Data Management) service. An unauthenticated attacker can inject control characters into the SUPI parameter, causing UDM to forward a malformed request to UDR and return a 500 Internal Server Error response that exposes internal infrastructure details. This vulnerability is fixed in 4.2.2.

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CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS — Exploit Prediction

0.0028

Probability of exploitation

0.19%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-20 Improper Input Validation

CWE-209 CWE-209

Affected Products

Vendor	Product	Versions
free5gc	free5gc	< 4.2.2

References

Advisories & Patches

https://github.com/free5gc/free5gc/security/advisories/GHSA-585v-hcgf-jhfr https://github.com/free5gc/free5gc/security/advisories/GHSA-585v-hcgf-jhfr

Exploits

https://github.com/free5gc/free5gc/security/advisories/GHSA-585v-hcgf-jhfr https://github.com/free5gc/free5gc/security/advisories/GHSA-585v-hcgf-jhfr

Frequently Asked Questions

What is CVE-2026-42459? +

free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, the free5GC UDM component fails to validate the supi path parameter in six GET handlers of the nudm-sdm (Subscriber Data Management) service. An unauthenticated attacker can inject control characters into the SUPI parameter, causing UDM to forward a malformed request to UDR and return a 500 Internal Server Error response that exposes internal infrastructure details. This vulnerability is fixed in 4.2.2. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-42459? +

CVE-2026-42459 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0028, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-42459? +

CVE-2026-42459 affects products from free5gc, specifically: free5gc. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-42459? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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