# CVE-2022-48935: linux: In the Linux kernel, the following vulnerability has been resolved:  netfilter: nf_tables: unregister flowtable hooks...

CVE-2022-48935 is fixed in linux on 1 platform, first by DEBIAN-CVE-2022-48935, released August 22, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2022-48935
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0021
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 22, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  netfilter: nf_tables: unregister flowtable hooks on netns exit  Unregister flowtable hooks before they are releases via nf_tables_flowtable_destroy() otherwise hook core reports UAF.  BUG: KASAN: use-after-free in nf_hook_entries_grow+0x5a7/0x700 net/netfilter/core.c:142 net/netfilter/core.c:142 Read of size 4 at addr ffff8880736f7438 by task syz-executor579/3666  CPU: 0 PID: 3666 Comm: syz-executor579 Not tainted 5.16.0-rc5-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace:  <TASK>  __dump_stack lib/dump_stack.c:88 [inline]  __dump_stack lib/dump_stack.c:88 [inline] lib/dump_stack.c:106  dump_stack_lvl+0x1dc/0x2d8 lib/dump_stack.c:106 lib/dump_stack.c:106  print_address_description+0x65/0x380 mm/kasan/report.c:247 mm/kasan/report.c:247  __kasan_report mm/kasan/report.c:433 [inline]  __kasan_report mm/kasan/report.c:433 [inline] mm/kasan/report.c:450  kasan_report+0x19a/0x1f0 mm/kasan/report.c:450 mm/kasan/report.c:450  nf_hook_entries_grow+0x5a7/0x700 net/netfilter/core.c:142 net/netfilter/core.c:142  __nf_register_net_hook+0x27e/0x8d0 net/netfilter/core.c:429 net/netfilter/core.c:429  nf_register_net_hook+0xaa/0x180 net/netfilter/core.c:571 net/netfilter/core.c:571  nft_register_flowtable_net_hooks+0x3c5/0x730 net/netfilter/nf_tables_api.c:7232 net/netfilter/nf_tables_api.c:7232  nf_tables_newflowtable+0x2022/0x2cf0 net/netfilter/nf_tables_api.c:7430 net/netfilter/nf_tables_api.c:7430  nfnetlink_rcv_batch net/netfilter/nfnetlink.c:513 [inline]  nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:634 [inline]  nfnetlink_rcv_batch net/netfilter/nfnetlink.c:513 [inline] net/netfilter/nfnetlink.c:652  nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:634 [inline] net/netfilter/nfnetlink.c:652  nfnetlink_rcv+0x10e6/0x2550 net/netfilter/nfnetlink.c:652 net/netfilter/nfnetlink.c:652  __nft_release_hook() calls nft_unregister_flowtable_net_hooks() which only unregisters the hooks, then after RCU grace period, it is guaranteed that no packets add new entries to the flowtable (no flow offload rules and flowtable hooks are reachable from packet path), so it is safe to call nf_flow_table_free() which cleans up the remaining entries from the flowtable (both software and hardware) and it unbinds the flow_block.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.16.12-1 | [DEBIAN-CVE-2022-48935](https://patchblox.com/security/data/fix/linux/debian-cve-2022-48935.md) | Aug 22, 2024 |
| Linux | linux Debian 13.5 (trixie) | 5.16.12-1 | [DEBIAN-CVE-2022-48935](https://patchblox.com/security/data/fix/linux/debian-cve-2022-48935.md) | Aug 22, 2024 |
| Linux | linux Debian 14 | 5.16.12-1 | [DEBIAN-CVE-2022-48935](https://patchblox.com/security/data/fix/linux/debian-cve-2022-48935.md) | Aug 22, 2024 |

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