# CVE-2021-47394: linux: In the Linux kernel, the following vulnerability has been resolved:  netfilter: nf_tables: unlink table before deleti...

CVE-2021-47394 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-47394, released May 21, 2024. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2021-47394
- Priority: High
- CVSS: 7.8 (high)
- EPSS: 0.0024
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 21, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  netfilter: nf_tables: unlink table before deleting it  syzbot reports following UAF: BUG: KASAN: use-after-free in memcmp+0x18f/0x1c0 lib/string.c:955  nla_strcmp+0xf2/0x130 lib/nlattr.c:836  nft_table_lookup.part.0+0x1a2/0x460 net/netfilter/nf_tables_api.c:570  nft_table_lookup net/netfilter/nf_tables_api.c:4064 [inline]  nf_tables_getset+0x1b3/0x860 net/netfilter/nf_tables_api.c:4064  nfnetlink_rcv_msg+0x659/0x13f0 net/netfilter/nfnetlink.c:285  netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2504  Problem is that all get operations are lockless, so the commit_mutex held by nft_rcv_nl_event() isn't enough to stop a parallel GET request from doing read-accesses to the table object even after synchronize_rcu().  To avoid this, unlink the table first and store the table objects in on-stack scratch space.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.14.12-1 | [DEBIAN-CVE-2021-47394](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47394.md) | May 21, 2024 |
| Linux | linux Debian 13.5 (trixie) | 5.14.12-1 | [DEBIAN-CVE-2021-47394](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47394.md) | May 21, 2024 |
| Linux | linux Debian 14 | 5.14.12-1 | [DEBIAN-CVE-2021-47394](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47394.md) | May 21, 2024 |

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