CVE-2026-40249 free5gc UDR fail-open request handling in PolicyDataSubsToNotifySubsIdPut may allow unintended subscription updates after input errors
Attackers can modify Policy Data notification subscriptions in free5GC UDR by exploiting fail-open error handling that continues execution despite invalid input.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-40249?
CVE-2026-40249 is a medium-severity vulnerability in Free5gc Free5gc, published on 16 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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 initialized PolicyDataSubscription object. This fail-open behavior may allow unintended modification of existing Policy Data notification subscriptions with invalid or empty input, depending on downstream processor and storage behavior. A patched version was not available at the time of publication.
Which versions are affected by CVE-2026-40249?
3 open source packages ship an affected version, including github.com/free5gc/udr. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/free5gc/udr Go | All versions | None |
github.com/free5gc/udr Go | All versions to 1.4.2 | None |
github.com/free5gc/udr Go | All versions to 1.4.2 | None |
Products include Free5gc Free5gc.
How do I fix CVE-2026-40249?
No fix published yet.
Is CVE-2026-40249 being exploited?
There is no known exploitation of CVE-2026-40249 in the wild and no public exploit code.
Other vulnerabilities in Free5gc Free5gc
- CVE-2026-44327 free5GC: NEF nnef-oam route group is unauthenticated; no-token requests reach the OAM handler
- CVE-2026-44329 free5GC's SMF UPI management interface lacks auth middleware; unauthenticated topology read/write requests reach handlers
- CVE-2026-44330 free5GC's NEF nnef-pfdmanagement API is unauthenticated; forged bearer tokens can read PFD data and create/delete PFD subscriptions
- CVE-2025-63679 Memory corruption in n/a
- CVE-2026-44315 free5GC's NEF 3gpp-pfd-management API is unauthenticated; forged bearer tokens can create, read, and delete PFD transactions
Sources
Also known as GHSA-gx38-8h33-pmxr, GO-2026-5407.