CVE-2026-40249: free5GC is an open-source implementation of the 5G core network

Q: How do I fix CVE-2026-40249?

free5gc: upgrade to newer than 4.2.1. Exact commands for each OS are on this page.

Q: Is CVE-2026-40249 being exploited?

CVE-2026-40249 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-40249 affect?

CVE-2026-40249 affects free5gc. Severity is medium (CVSS 5.3). free5GC is an open-source implementation of the 5G core network. In versions 4.2.1 and below of the UDR service, the PUT handler for updating Policy Data notification subscriptions at /nudr-dr/v2/policy-data/subs-to-notify/{subsId} does not

Q: How urgent is CVE-2026-40249?

Priority 35/100. Public exploit reference; Remotely exploitable, no login, no user action

This week

MEDIUM 5.3REMOTEUPGRADE

CVE-2026-40249 is a medium-severity flaw (CVSS 5.3) affecting free5gc. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

free5GC is an open-source implementation of the 5G core network. In versions 4.2.1 and below of the UDR service, the PUT handler for updating Policy Data notification subscriptions at /nudr-dr/v2/policy-data/subs-to-notify/{subsId} does not return after request body retrieval or deserialization errors. Although HTTP 500 or 400 error responses are sent, execution continues and the processor is invoked with a potentially uninitialized or partially

Why this priority

Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 75%)
CISA exploited list	No
Weakness	CWE-636, CWE-754
Published	2026-04-16
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: free5gc

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-16 22:16 UTCPublished CVE record published
2026-06-17 10:44 UTCUpdated Record last modified

free5gc free5gc UPGRADE

Affected: <= 4.2.1

Fixed in: newer than 4.2.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy free5gc || rpm -q free5gc || free5gc --version

2. UPGRADE to newer than 4.2.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade free5gc

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade free5gc

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-40249?

free5gc: upgrade to newer than 4.2.1. Exact commands for each OS are on this page.

Is CVE-2026-40249 being exploited?

CVE-2026-40249 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-40249 affect?

CVE-2026-40249 affects free5gc. Severity is medium (CVSS 5.3). free5GC is an open-source implementation of the 5G core network. In versions 4.2.1 and below of the UDR service, the PUT handler for updating Policy Data notification subscriptions at /nudr-dr/v2/policy-data/subs-to-notify/{subsId} does not

How urgent is CVE-2026-40249?

Priority 35/100. Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-40343 MEDIUM 5.8 UPGRADE UPGRADE free5GC UDR is the user data repository (UDR) for free5GC, an an open-source project for 5th generation (5G) m
CVE-2026-41135 HIGH 7.5 UPGRADE UPGRADE free5GC UDR is the Policy Control Function (PCF) for free5GC, an an open-source project for 5th generation (5G
CVE-2026-41136 MEDIUM 5.3 UPGRADE UPGRADE free5GC AMF provides Access & Mobility Management Function (AMF) for free5GC, an an open-source project for 5t
CVE-2026-44329 CRITICAL 10.0 UPGRADE free5GC is an open-source implementation of the 5G core network
CVE-2026-44327 CRITICAL 10.0 UPGRADE free5GC is an open-source implementation of the 5G core network

References

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