CVE-2026-42083: free5gc Auth Bypass — Exploit & Fix

Description

free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, PCF Npcf_SMPolicyControl missing authentication middleware allows unauthenticated access to SM policy handlers and disclosure of subscriber SUPI. In NewServer(), the smPolicyGroup route group is created and routes are applied without attaching the router authorization middleware. In contrast, other PCF service groups such as Npcf_PolicyAuthorization do attach RouterAuthorizationCheck before route registration. Because the middleware is missing, requests to the /npcf-smpolicycontrol/v1/sm-policies, /npcf-smpolicycontrol/v1/sm-policies/{smPolicyId}, /npcf-smpolicycontrol/v1/sm-policies/{smPolicyId}/update, and /npcf-smpolicycontrol/v1/sm-policies/{smPolicyId}/delete endpoints can reach business logic even when no valid OAuth token is provided. This vulnerability is fixed in 4.2.2.

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CVSS v3.1 Score

8.2

HIGH

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

EPSS — Exploit Prediction

0.0031

Probability of exploitation

0.22%

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-862 Missing Authorization

Affected Products

Vendor	Product	Versions
free5gc	free5gc	< 4.2.2

References

Advisories & Patches

https://github.com/free5gc/free5gc/security/advisories/GHSA-6rgm-gr97-x3j5 https://github.com/free5gc/pcf/commit/8c4d457cdf58bb239ee30e88c56b370b22073964 https://github.com/free5gc/pcf/pull/63 https://github.com/free5gc/free5gc/security/advisories/GHSA-6rgm-gr97-x3j5

Exploits

https://github.com/free5gc/free5gc/issues/844 https://github.com/free5gc/free5gc/issues/844

Frequently Asked Questions

What is CVE-2026-42083? +

free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, PCF Npcf_SMPolicyControl missing authentication middleware allows unauthenticated access to SM policy handlers and disclosure of subscriber SUPI. In NewServer(), the smPolicyGroup route group is created and routes are applied without attaching the router authorization middleware. In contrast, other PCF service groups such as Npcf_PolicyAuthorization do attach RouterAuthorizationCheck before route registration. Because the middleware is missing, requests to the /npcf-smpolicycontrol/v1/sm-policies, /npcf-smpolicycontrol/v1/sm-policies/{smPolicyId}, /npcf-smpolicycontrol/v1/sm-policies/{smPolicyId}/update, and /npcf-smpolicycontrol/v1/sm-policies/{smPolicyId}/delete endpoints can reach business logic even when no valid OAuth token is provided. This vulnerability is fixed in 4.2.2. It has a CVSS v3.1 base score of 8.2 (HIGH).

How severe is CVE-2026-42083? +

CVE-2026-42083 has a CVSS v3.1 score of 8.2 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0031, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-42083? +

CVE-2026-42083 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-2026-42083? +

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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